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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Mar. 09, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	ARPO
Entity Well Known Seasoned Issuer	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Registrant Name	Aerpio Pharmaceuticals, Inc.
Entity Central Index Key	0001422142
Entity Public Float			$ 25,975,518
Entity Common Stock, Shares Outstanding		40,588,004
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity File Number	001-38560
Entity Tax Identification Number	61-1547850
Entity Address, Address Line One	9987 Carver Road
Entity Address, City or Town	Cincinnati
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45242
City Area Code	513
Local Phone Number	985-1920
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s Definitive Proxy Statement relating to the Annual Meeting of Shareholders are incorporated by reference into Part III of this Report. Such Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2019.

Consolidated Balance Sheets - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 38,524,536	$ 62,614,010
Prepaid research and development contracts	311,154	754,392
Other current assets	734,785	615,681
Total current assets	39,570,475	63,984,083
Furniture and equipment, net	164,187	98,449
Operating lease right-of-use assets, net	162,124
Deposits	40,000	40,960
Total assets	39,936,786	64,123,492
Current liabilities:
Accounts payable and accrued expenses	3,231,450	5,456,917
Current portion of operating lease liability	102,555
Total current liabilities	3,334,005	5,456,917
Operating lease liability, net of current portion	67,438
Total liabilities	3,401,443	5,456,917
Commitments and contingencies (Note 11)
Stockholders’ equity:
Common stock, $0.0001 par value per share; 300,000,000 shares authorized and 40,588,004 shares issued and outstanding at December 31, 2019 and 2018.	4,059	4,059
Additional paid-in capital	178,766,806	177,621,807
Accumulated deficit	(142,235,522)	(118,959,291)
Total stockholders’ equity	36,535,343	58,666,575
Total liabilities and stockholders’ equity	$ 39,936,786	$ 64,123,492

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	40,588,004	40,588,004
Common stock, shares outstanding	40,588,004	40,588,004

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
License revenue, and other		$ 20,157,430
Type of Revenue [Extensible List]		arpo:LicenseRevenueAndOtherMember
Operating expenses
Research and development	$ 12,824,402	$ 17,852,756
General and administrative	9,756,185	13,485,918
Restructuring expense	1,863,495
Total operating expenses	24,444,082	31,338,674
Loss from operations	(24,444,082)	(11,181,244)
Grant income	142,729	6,394
Interest income	1,030,839	778,215
Total other income	1,173,568	784,609
Net and comprehensive loss	$ (23,270,514)	$ (10,396,635)
Net and comprehensive loss per share
Basic and diluted	$ (0.57)	$ (0.31)
Weighted average number of common shares used in computing net loss per share attributable to common stockholders, basic and diluted	40,588,004	33,930,846

Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2017	$ 17,435,489	$ 2,707	$ 125,995,438	$ (108,562,656)
Balance, Shares at Dec. 31, 2017		27,070,038
Issuance of restricted stock		$ 6	(6)
Issuance of restricted stock, Shares		60,000
Issuance of common stock, net of issuance costs	48,119,027	$ 1,341	48,117,686
Issuance of common stock, net of issuance costs, Shares		13,408,200
Issuance of common stock upon exercise of stock options	$ 76,832	$ 5	76,827
Issuance of common stock upon exercise of stock options, Shares	52,099	52,099
Forfeiture of restricted stock, Shares		(2,333)
Share-based compensation expense	$ 3,431,862		3,431,862
Net and comprehensive loss	(10,396,635)			(10,396,635)
Balance at Dec. 31, 2018	58,666,575	$ 4,059	177,621,807	(118,959,291)
Balance, Shares at Dec. 31, 2018		40,588,004
Issuance of warrants	$ 53,440		53,440
Cumulative effect of change in accounting principle			5,717	(5,717)
Issuance of common stock upon exercise of stock options, Shares	0
Share-based compensation expense	$ 1,085,842		1,085,842
Net and comprehensive loss	(23,270,514)			(23,270,514)
Balance at Dec. 31, 2019	$ 36,535,343	$ 4,059	$ 178,766,806	$ (142,235,522)
Balance, Shares at Dec. 31, 2019		40,588,004

Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2018 USD ($)
Statement Of Stockholders Equity [Abstract]
Issuance costs	$ 3,502,543

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net and comprehensive loss	$ (23,270,514)	$ (10,396,635)
Adjustments to reconcile net and comprehensive loss to net cash used in operating activities:
Depreciation	76,501	46,686
Loss on disposal of assets	94,713
Consulting expenses related to warrants	53,440
Stock-based compensation	1,085,842	3,431,862
Changes in operating assets and liabilities:
Prepaid research and development contracts	443,238	(441,252)
Other current assets	(119,104)	(293,460)
Deposits	960	(20,000)
Accounts payable and accrued expenses	(2,217,598)	1,864,753
Net cash used in operating activities	(23,852,522)	(5,808,046)
Investing activities:
Purchase of furniture and equipment	(236,952)	(37,912)
Net cash used in investing activities	(236,952)	(37,912)
Financing activities:
Proceeds from exercise of stock options		76,832
Proceeds from sale of common stock		51,621,570
Cash paid in connection with the sale of common stock		(3,502,543)
Net cash provided by financing activities		48,195,859
Net (decrease) increase in cash and cash equivalents	(24,089,474)	42,349,901
Cash and cash equivalents at beginning of year	62,614,010	20,264,109
Cash and cash equivalents at end of year	$ 38,524,536	$ 62,614,010

Nature of Organization and Operations

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Organization and Operations

1.	Nature of Organization and Operations

Aerpio Pharmaceuticals, Inc. (the “Company”) is a biopharmaceutical company focused on developing compounds that activate Tie2 to treat ocular diseases and diabetic complications. The Company was incorporated as Zeta Acquisition Corp. II (“Zeta”) in the State of Delaware on November 16, 2007. Zeta was a “shell company” (as defined in Rule 12b-2 of the Securities Exchange Act of 1934, as amended).

The Company’s pipeline includes the humanized monoclonal antibody, ARP-1536, directed at the same target as subcutaneous AKB-9778, is in preclinical development. The Company is evaluating development options for ARP-1536, including subcutaneous injection for the treatment of diabetic vascular complications, e.g., diabetic nephropathy and intravitreal injection as an adjunctive therapy for diabetic macular edema.

The Company is also developing a bispecific antibody that binds both VEGF and VE-PTP which is designed to inhibit VEGF activation and activate Tie2. The Company believes this bispecific antibody has the potential to be an improved treatment for wet aged-related macular degeneration (“AMD”) and diabetic macular edema via intravitreal injection.

In two consecutive trials, TIME-2 and TIME-2b, subcutaneous AKB-9778 showed reduction in Urine Albumin-Creatinine Ratio (“UACR”), a measure of progression of diabetic kidney disease. The Company believes that systemic treatment with AKB-9778 could have the potential to change the treatment paradigm for diabetics in the future and potentially address a major societal problem by lowering the cost of care associated generally with diabetes.

Based on the preclinical proof of concept and the results of the Phase 1b trial showing a reduction in intraocular pressure (“IOP”) in patients with ocular hypertension (“OHT”) and open angle glaucoma (“OAG”), the Company plans to further advance the glaucoma program into a Phase 2 clinical trial with results expected in the first quarter of 2021.

In June 2018, the Company licensed AKB-4924, a selective stabilizer of hypoxia-inducible factor-1 alpha (“HIF-1 alpha”) to Gossamer Bio, Inc. (“Gossamer”) AKB-4924, (now called GB004), is being developed for the treatment of inflammatory bowel disease (“IBD”). HIF-1 alpha is involved in mucosal wound healing and the reduction of inflammation in the gastrointestinal tract. Gossamer has completed the Phase 1 multiple ascending dose (“MAD”) clinical study and is currently running a Phase 1b clinical study in ulcerative colitis patients. Gossamer is expected to have results of the Phase 1b study in ulcerative colitis patients in the first half of 2020. Gossamer is responsible for all remaining development and commercial activities for GB004.

On June 28, 2018, the Company closed an underwritten public offering for the sale of 11,688,000 shares of its common stock, and subsequently on July 2, 2018, the Company closed on the sale of an additional 1,720,200 shares of its common stock, pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock (the “2018 Offering”). In the aggregate, the Company received net proceeds of $48.1 million from the 2018 Offering after a deduction of $3.5 million related to underwriting discounts and commissions and offering expenses paid in conjunction with the 2018 Offering.

The Company’s operations to date have been limited to organizing and staffing the Company, business planning, raising capital, acquiring and developing its technology, identifying potential product candidates and undertaking preclinical and clinical studies. The Company’s revenue has been primarily limited to license revenue from Gossamer Bio. Inc., GB004, Inc. (collectively “Gossamer”). Future revenue is dependent on the terms of the license agreement with Gossamer Bio., Inc. as further described in Note 15. The Company’s product candidates are subject to long development cycles and there is no assurance the Company will be able to successfully develop, obtain regulatory approval for, or market its product candidates.

The Company is subject to a number of risks similar to other life science companies in the current stage of its life cycle including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of any of the Company’s products that are approved, and protection of proprietary technology. If the Company does not successfully commercialize any of its products or mitigate any of these other risks, it will be unable to generate revenue or achieve profitability.

The Company incurred losses from operations and had a negative cash flows from operating activities for the years ended December 31, 2019 and 2018 (and since inception). The Company’s current operating plan indicates that it will continue to incur losses from operations and generate negative cash flows from operating activities given ongoing expenditures related to the completion of its ongoing clinical trials and the Company’s lack of product revenue generating activities. However, the Company believes it has the ability to control its current operating plan and that existing cash and cash equivalents of approximately $38.5 million at December 31, 2019 will be sufficient to allow the Company to fund its current operating plan into at least the second quarter of 2021, and as a result, through at least twelve months from the filing of the Company’s 2019 Annual Report on Form 10-K.

There can be no assurance, however, that the current operating plan will be achieved in the time frame anticipated by the Company, or that its cash resources will fund the Company’s operating plan for the period anticipated by the Company or that additional funding will be available on terms acceptable to the Company, or at all. The Company will need to raise additional funds in order to further advance its clinical research programs, commence additional clinical trials, and operate its business and meet its obligations as they come due. The Company is pursuing financing alternatives, which include permanent equity financing, business development arrangements, and licensing arrangements. However, financing may not be available to the Company in the necessary time frame, in amounts that the Company requires, on terms that are acceptable to the Company, or at all. If the Company raises additional funds through collaboration, licensing or other similar arrangements, it may be necessary to relinquish valuable rights to its potential products or proprietary technologies or grant licenses on terms that are not favorable to the Company. If the Company is unable to raise the necessary funds when needed or reduce spending on currently planned activities, it may not be able to continue the development of its product candidates or the Company could be required to delay, scale back, or eliminate some or all of its development programs and other operations and will materially harm its business, financial position and results of operations.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements have been prepared in accordance with U.S. Securities and Exchange Commission (“SEC”) regulations and include all of the information and disclosures required by U.S. generally accepted accounting principles ("U.S. GAAP" or "GAAP"). Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

The Company’s consolidated financial statements are stated in U.S. dollars.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing proprietary therapeutics. All the assets and operations of the Company are located in the U.S.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results may differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: prepaid and accrued research and development expense, stock-based compensation expense, revenue recognition and income taxes.

Cash and Cash Equivalents

Cash and cash equivalents consist of all cash on hand and $100,000 invested in short-term certificates of deposits with original maturities of three months or less at the time of purchase. At December 31, 2019 and 2018, the Company’s cash equivalents are primarily in money market funds. The Company maintains balances with its banks in excess of federally insured limits.

Revenue Recognition

At the inception of an arrangement, the Company evaluates if a counterparty to a contract is a customer, if the arrangement is within the scope of revenue from contracts with customers guidance and the term of the contract. The Company recognizes revenue when its customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies the following five-step model in order to determine this amount: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation. The Company recognizes the amount of the transaction price as revenue that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied.

The Company enters into collaboration arrangements, under which it licenses certain rights to its intellectual property to third parties. The terms of these agreements may include payment to the Company of one or more of the following: nonrefundable upfront license fees; development, sale and commercial milestone payments and royalties on net sales of licensed products. Each of these types of payments are classified as license revenue except for revenue from royalties on net sales of licensed products, which are classified as royalty revenue.

For each collaboration agreement that results in revenues, the Company identifies all material promised goods and services, which may include a license to intellectual property, research and development activities and/or transition activities. Promised goods or services are considered to be separate performance obligations if they are distinct. In order to determine the transaction price to be allocated to each performance obligation, in addition to any upfront payment, the Company estimates the amount of variable consideration at the outset of the contract either utilizing the expected value or most likely amount method, depending on the facts and circumstances relative to the contract. The Company constrains (reduces) the estimates of variable consideration such that it is probable that a significant reversal of previously recognized revenue will not occur throughout the life of the contract. When determining if variable consideration should be constrained, management considers whether there are factors outside the Company’s control that could result in a significant reversal of revenue. In making these assessments, the Company considers the likelihood and magnitude of a potential reversal of revenue. These estimates are re-assessed each reporting period as required.

Once the estimated transaction price is established, amounts are allocated to the performance obligations that have been identified. The transaction price is generally allocated to each separate performance obligation on a relative standalone selling price basis. The Company must develop assumptions that require judgment to determine the standalone selling price (“SSP”) in order to account for these agreements. To determine the standalone selling price the Company’s assumptions may include (i) assumptions regarding the probability of obtaining marketing approval for the drug candidate; (ii) estimates regarding the timing of and the expected costs to develop and commercialize the drug candidate; (iii) estimates of future cash flows from potential product sales with respect to the drug candidate; and (iv) appropriate discount and tax rates. Standalone selling prices used to perform the initial allocation are not updated after contract inception. The Company does not include a financing component to its estimated transaction price at contract inception unless it estimates that certain performance obligations will not be satisfied within one year.

Upfront License Fees

If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, upfront license fees based on the relative value prescribed to the license compared to the total value of the arrangement. The revenue is recognized when the license is transferred to the collaborator and the collaborator is able to use and benefit from the license. For licenses that are not distinct from other obligations identified in the arrangement, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. If the combined performance obligation is satisfied over time, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Development Milestone Payments

Depending on facts and circumstances, the Company may conclude it is appropriate to include the milestone in the estimated transaction price using the most likely amount method or it is appropriate to fully constrain the milestone. A milestone payment is included in the transaction price in the reporting period the Company concludes that it is probable that recording revenue in the period will not result in a significant reversal in amounts recognized in future periods. The Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes that achievement of the milestone is probable and that recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records a corresponding contract asset when this conclusion is reached. Milestone payments that have not been included in the transaction price to date are fully constrained. These milestones remain fully constrained until the Company concludes that achievement of the milestone is probable and recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company re-evaluates the probability of achievement of such development milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that it has recorded, if necessary.

Sales-based Milestone and Royalty Payments

The Company’s collaborators may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the license to the Company’s intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate.

Grant Income

Grant income is recognized as earned based on contract work performed.

Research and Development

Research and development costs are expensed as incurred. Research and development expense consists of (i) employee-related expenses, including salaries, benefits, travel and stock-based compensation expense; (ii) external research and development expenses incurred under arrangements with third parties, such as contract research organizations and consultants; (iii) the cost of acquiring, developing and manufacturing clinical study materials; and (iv) costs associated with clinical, preclinical and regulatory activities.

The Company enters into consulting, research, and other agreements with commercial firms, researchers, universities and others for the provision of goods and services. Under such agreements, the Company may pay for services on a monthly, quarterly, project or other basis. Such arrangements are generally cancellable upon reasonable notice and payment of costs incurred. Costs are considered incurred based on an evaluation of the progress to completion of specific tasks under each contract using information and data provided to the Company by its clinical sites and vendors. These costs consist of direct and indirect costs associated with specific projects, as well as fees paid to various entities that perform certain research on behalf of the Company.

Patents

Costs incurred in connection with the application for and issuances of patents are expensed as incurred.

Income Taxes

Income taxes are recorded in accordance with ASC Topic 740, Income Taxes (“ASC 740”) which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the consolidated financial statement and tax bases of assets and liabilities and for loss and credit carryforwards using enacted tax rates anticipated to be in effect for the year in which the differences are expected to reverse. Valuation allowances are provided, if, based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position, as well as consideration of the available facts and circumstances. As of December 31, 2019 and 2018, the Company does not have any uncertain tax positions. The Company recognizes interest and penalties related to uncertain tax positions, if any exist, in income tax expense.

Net Loss and Comprehensive Loss per Share Attributable to Common Stockholders

The Company’s basic net and comprehensive loss per share attributable to common stockholders is calculated by dividing the net and comprehensive loss by the weighted average number of shares of common stock outstanding for the period. The diluted net and comprehensive loss per share attributable to common stockholders is computed by adjusting the weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury stock method.

Stock-Based Compensation

The Company accounts for its stock-based compensation awards in accordance with ASC Topic 718, Compensation – Stock Compensation (“ASC 718”). ASC 718 requires all stock-based payments to employees, including grants of employee stock options and restricted stock, to be recognized in the consolidated statements of operations and comprehensive loss based on their fair values. All the Company’s stock-based awards are subject only to service-based vesting conditions. The Company estimates the fair value of its stock-based awards using the Black-Scholes option pricing model, which requires the input of assumptions, including (a) the expected stock price volatility, (b) the calculation of expected term of the award, (c) the risk-free interest rate and (d) expected dividends. The fair value of restricted stock awards is determined based on the Company’s estimated common stock value.

Due to the historical lack of a public market for the trading of the Company’s common stock and a lack of company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The computation of expected volatility is based on the historical volatility of a representative group of companies with similar characteristics to the Company, including stage of product development and life science industry focus. The Company believes the group selected has sufficient similar economic and industry characteristics and includes companies that are most representative of the Company.

The Company uses the simplified method as prescribed by the SEC Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term, as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term for options granted to employees, and utilizes the contractual term for options granted to non-employees. The expected term is applied to the stock option grant group as a whole, as the Company does not expect substantially different exercise or post-vesting termination behavior among its employee population. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected life of the stock options.

Compensation expense related to awards to employees is calculated on a straight-line basis by recognizing the grant date fair value over the associated service period of the award, which is generally the vesting term.

Fair Value of Financial Instruments

The Company’s financial instruments consist of cash and cash equivalents, accounts payable and accrued expenses. The Company values cash equivalents using quoted market prices. The fair value of accounts payable and accrued expenses approximates its carrying value because of its short-term nature.

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC Topic 820, Fair Value Measurements and Disclosures (“ASC 820”) establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available.

Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below:

•

Level 1 – Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date

•

Level 2 – Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly

•

Level 3 – Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable

To the extent that a valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no transfers within the fair value hierarchy in the years ended December 31, 2019 and 2018. The assets of the Company measured at fair value on a recurring basis as of December 31, 2019 and 2018 are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
December 31, 2019
Assets:
Cash and cash equivalents	$	38,524,536	$	—	$	—	$	38,524,536
Total assets	$	38,524,536	$	—	$	—	$	38,524,536
December 31, 2018
Assets:
Cash and cash equivalents	$	62,614,010	$	—	$	—	$	62,614,010
Total assets	$	62,614,010	$	—	$	—	$	62,614,010

Concentrations of Credit Risk and Off-Balance Sheet Risk

Cash and cash equivalents are the only financial instruments that potentially subject the Company to concentrations of credit risk. At December 31, 2019 and 2018, the Company maintains its cash and cash equivalents with high-quality, accredited financial institutions and, accordingly, such funds are subject to minimal credit risk. The Company has no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts, or other hedging arrangements.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources, if any. Comprehensive loss equaled net loss for all periods presented.

Furniture and Equipment

Furniture and equipment is stated at cost, less accumulated depreciation. Furniture and equipment is depreciated using the straight-line method over the estimated useful lives of the assets, generally three to seven years. Such costs are periodically reviewed for recoverability when impairment indicators are present. Such indicators include, among other factors: operating losses, unused capacity, market value declines and technological obsolescence. Recorded values of asset groups of furniture and equipment that are not expected to be recovered through undiscounted future net cash flows are written down to current fair value, which generally is determined from estimated discounted future net cash flows (assets held for use) or net realizable value (assets held for sale).

Leases

At the inception of an arrangement the Company determines whether the arrangement is or contains a lease based on the circumstances present. All leases with a term greater than one year are recognized on the consolidated balance sheet as right-of-use assets, lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize on the consolidated balance sheet leases with terms of one-year or less. Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company utilizes the appropriate incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

In February 2016, the FASB issued ASU No. 2016-02, Leases, to enhance the transparency and comparability of financial reporting related to leasing arrangements. Under this new lease standard, leases are required to be recognized on the balance sheet as right-of-use assets and operating lease liabilities. Disclosure requirements have been enhanced with the objective of enabling financial statement users to assess the amount, timing, and uncertainty of cash flows arising from leases. The Company adopted the new guidance on January 1, 2019. See additional discussion in Note 11.

In July 2018, the FASB issued ASU 2018-11, Leases, Targeted Improvements, (“ASU 2018-11”), which contains certain amendments to ASU 2016-02 intended to provide relief in implementing the new standard. ASU 2018-11 provides registrants with an option to not restate comparative periods presented in the financial statements. The Company adopted this new standard on January 1, 2019 (the “adoption date”) using a cumulative-effect adjustment on the effective date of the standard, for which comparative periods are presented in accordance with the previous guidance in ASC 840, Leases. In adopting the new standard, the Company elected to utilize the available package of practical expedients permitted under the transition guidance within the new standard The expedients used by the Company are as follows: (1) allowing an entity to not reassess the lease classification for any expired or existing leases, (2) allowing an entity to not reassess the treatment of initial direct costs as they related to existing leases, and (3) allowing an entity to not reassess whether expired or existing contracts are or contain leases. The Company adopted the new guidance on January 1, 2019. See additional discussion in Note 11.

In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 improves financial reporting for share-based payments issued to nonemployees under ASC 718 by expanding the scope of the employee share-based payments guidance to include share-based payments issued to nonemployees. The amendments in ASU 2018-07 are effective for public companies for fiscal years beginning after December 31, 2018, including interim periods within that fiscal year. The Company adopted ASU 2018-07 as of January 1, 2019 and recorded a one-time cumulative adjustment of $5,717 upon adoption.

No other new accounting pronouncement recently issued or newly effective had or is expected to have a material impact on the Company’s consolidated financial statements.

Accounts Payable and Accrued Expenses

12 Months Ended

Dec. 31, 2019

Payables And Accruals [Abstract]

Accounts Payable and Accrued Expenses

3. Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following as of:

	December 31,
	2019		2018
Accounts payable	$	439,785	$	595,680
Restructuring accrual (see Note 16)		793,913		—
Professional fees		346,999		487,923
Accrued bonus		689,830		1,877,455
Accrued retention bonus		521,859		—
Accrued vacation		43,470		90,663
Accrued project costs		382,131		2,232,014
Other		13,463		173,182
Total accounts payable and accrued expenses	$	3,231,450	$	5,456,917

Furniture and Equipment

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Furniture and Equipment

4. Furniture and Equipment

Furniture and equipment consist of the following as of:

	December 31,
	2019			2018
Furniture	$	154,669		$	156,928
Computers		56,443			75,716
Equipment		246,056			141,067
Leasehold improvements		35,869			35,869
Total furniture and equipment		493,037			409,580
Accumulated depreciation		(328,850	)		(311,131	)
Furniture and equipment, net	$	164,187		$	98,449

Common Stock

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Common Stock

5. Common Stock

As of December 31, 2019 and 2018, the Company had 300,000,000 shares of authorized common stock with par value of $0.0001 per share.

The common stock has the following characteristics:

Voting

The holders of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders and written actions in lieu of meetings.

Dividends

The holders of common stock are entitled to receive dividends, if and when declared by the Board of Directors. Since the Company’s inception, no dividends have been declared or paid to the holders of common stock.

Liquidation

In the event of any voluntary or involuntary liquidation, dissolution, or winding-up of the Company, the holders of common stock are entitled to share ratably in the Company’s assets.

Warrants to Purchase Common Stock

At December 31, 2019 and 2018, the Company had warrants outstanding for the purchase of 917,562 and 317,562 shares, respectively, of the Company’s common stock. In October 2019, the Company issued warrants for the purchase of 600,000 shares of the Company’s common stock at an exercise price of $0.486 per share in connection with the hiring of a strategic advisor consultant for a six-month period. These warrants vest in equal monthly installments over a six-month period beginning October 14, 2019 and expire on October 24, 2024. At the date of grant the fair value of these awards was determined using a Black-Scholes Merton pricing model. Included at December 31, 2019 and 2018 are warrants for the purchase of 317,562 shares of the Company’s common stock at an exercise price of $5.00 per share that were issued in connection with the 2017 Offering and have a three-year term expiring on March 15, 2020. At the expiration date of the warrants, if the fair value of the Company’s common stock exceeds the exercise price, the warrant will be automatically exercised and the exercise price will be fulfilled through the net share settlement provisions. The number of shares and the exercise price shall be adjusted for standard ant-dilution events such as stock splits, combinations, reorganizations, or issue shares as part of a common stock dividend. Upon a change of control, the warrant holder will have the right to receive securities, cash or other properties it would have been entitled to receive had the warrant been exercised. The warrants are equity classified instruments and do not contain contingent exercise provisions, or other features, that would preclude the Company from concluding that the warrants are indexed solely to the Company’s common stock.

Preferred Stock

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Preferred Stock

6. Preferred Stock

As of December 31, 2019 and 2018, the Company had 10,000,000 shares of preferred stock, par value $0.0001 per share, in authorized capital. No preferred stock was issued and outstanding at December 31, 2019 and 2018.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

In March 2017, the Company’s Board of Directors adopted, and the stockholders approved, the 2017 Stock Option and Incentive Plan (the “2017 Plan”), that became effective in April 2017. The 2017 Plan provides for the issuance of incentive awards up to 4,600,000 shares of common stock to officers, employees, consultants and directors, less the number of shares subject to issued and outstanding awards under the Company’s 2011 Equity Incentive Plan that were assumed in the Merger. The 2017 Plan also provides that the number of shares reserved for issuance thereunder will be increased annually on the first day of each year beginning in 2018 by four percent (4%) of the shares of our common stock outstanding on the last day of the immediately preceding year or such smaller increase as determined by our Board of Directors. As a result of the evergreen increase, a total of 1,623,520 shares were added to the 2017 Plan on January 1, 2019 and a total of 1,623,520 shares were added to the 2017 Plan on January 1, 2020.

Stock Options

The options granted generally vest over 48 months. Under the 2017 Plan, options vest in installments of 25% at the one-year anniversary and thereafter in 36 equal monthly installments beginning on the 1^st of the month after the one-year anniversary date, subject to the employee’s continuous service with the Company. In May 2019, the Company issued a special retention grant of options to purchase an aggregate of 2,419,050 shares of common stock which vest in installments of 50% at June 30, 2020 and 50% at June 30, 2021, subject to the employee’s continuous service with the Company. The options generally expire ten years after the date of grant. The fair value of the options at the date of grant is recognized as an expense over the requisite service period. During the years ended December 31, 2019 and 2018, 4,666,728 and 1,615,200 option awards were granted, respectively. All option awards granted during 2019 and 2018 were under the 2017 Equity Plan.

As of December 31, 2019 and 2018, 1,983,093 and 2,959,562 shares were reserved for issuance under the 2017 Plan, respectively.

The following table summarizes the stock option activity during the years ended December 31, 2019 and 2018:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding, January 1, 2018		1,912,980		$	3.72		8.24	$	2,738,704
Granted		1,615,200			3.64
Exercised		(52,099	)		1.47
Expired/cancelled		(124,949	)		3.23
Outstanding, December 31, 2018		3,351,132		$	3.73		8.24	$	142,788
Expected to vest, December 31, 2018		2,197,619		$	4.17		9.19	$	-
Options exercisable, December 31, 2018		1,153,513		$	2.90		6.37	$	142,788
Outstanding, January 1, 2019		3,351,132		$	3.73		8.24	$	142,788
Granted		4,666,728			1.85
Exercised		—
Expired/cancelled		(2,682,010	)		2.70
Outstanding, December 31, 2019		5,335,850		$	2.60		6.23	$	2,866
Expected to vest, December 31, 2019		2,395,265		$	1.93		9.00	$	2,866
Options exercisable, December 31, 2019		2,940,585		$	3.15		3.98	$	—

Aggregate intrinsic value represents the estimated fair value of the Company’s common stock at the end of the period in excess of the weighted average exercise price multiplied by the number of options outstanding or exercisable. The aggregate intrinsic value of the options at December 31, 2019 and 2018 was $2,866 and $142,788, respectively.

No stock options were exercised during 2019. Stock options exercised during 2018 had an intrinsic value of $139,108.

For the years ended December 31, 2019 and 2018, the Company recognized compensation expense for stock options of $1,085,842 and $2,982,173, respectively. During the fourth quarter of 2019, the Company recorded a one-time stock-based compensation cumulative reversal of $1,051,735 for the forfeitures of outstanding equity awards related to the Chief Executive Officer and Chief Financial and Business Officer who departed the Company on October 15, 2019. As of December 31, 2019, there was $2,309,337 of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted average period of 2.31 years.

The Company uses the Black-Scholes option pricing model to determine the estimated fair value for stock-based awards. For the years ended December 31, 2019 and 2018, there were 4,666,728 and 1,615,200 options granted out of the 2017 Plan, respectively. Option pricing models require the input of various assumptions, including the option’s expected life, expected dividend yield, price volatility and risk-free interest rate of the underlying stock. As there has not been significant public market activity of the Company’s Common Stock, the Company has determined the volatility assumption for options granted based on data from a peer group of companies that issued options with substantially similar terms. The expected volatility of options granted has been determined using the average of the historical volatility measures of this peer group of companies for a period equal to the expected life of the option. The risk-free interest rate is based on the rate applicable to U.S. Treasury zero-coupon issues, with remaining maturities commensurate with the expected term of the options granted in effect on the date of grant. The Company has not paid, and does not anticipate paying, cash dividends on shares of Common Stock; therefore, the expected dividend yield is assumed to be zero in the option valuation model. Accordingly, the weighted-average fair value of the options granted during the years ended December 31, 2019 and 2018, was $1.11 and $2.22, respectively. The calculation was based on the following assumptions.

	Year Ended December 31,
	2019			2018
Expected term (years)	5.36			6.07
Risk-free interest rate		2.24	%		2.85	%
Expected volatility		64.88	%		65.99	%
Expected dividend yield		—			—

Restricted Stock

Shares of restricted stock generally had similar vesting terms as stock options. A summary of the Company’s restricted stock activity and related information for the years ended December 31, 2019 and 2018 is as follows:

	Shares			Weighted Average Grant Date Fair Value
Nonvested, January 1, 2018		91,576		$	2.12
Granted		60,000			4.75
Vested		(149,243	)		3.18
Forfeited		(2,333	)		2.25
Nonvested, December 31, 2018		—		$	—

Nonvested, January 1, 2019		—		$	—
Granted		—			—
Vested		—			—
Forfeited		—			—
Nonvested, December 31, 2019		—		$	—

For the years ended December 31, 2019 and 2018, the Company recognized compensation expense for restricted stock of $0 and $449,689, respectively. As of December 31, 2019, all restricted stock had vested.

Compensation Expense Summary

The Company recognized the following compensation cost related to employee and non-employee stock-based compensation activity for the periods presented below.

	Year Ended December 31,
	2019		2018
Research and development	$	510,923	$	392,470
General and administrative		574,919		3,039,392
Total	$	1,085,842	$	3,431,862

The decrease in compensation expense during the year ended December 31, 2019, is primarily due to the cumulative reversal for the forfeitures of outstanding equity awards related to the Chief Executive Officer, Chief Financial and Business Officer and other employees who left the Company during 2019.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

8. Income Taxes

The Company did not record a current or deferred income tax expense or benefit for the years ended December 31, 2019 and 2018, due to the Company’s net and comprehensive losses and increases in its deferred tax asset valuation allowance. A reconciliation of the statutory federal income tax with the provision for income taxes are as follows:

	Year Ended December 31,
	2019			2018
Federal tax at statutory rate	(21.00%)			(21.00%)
State and local tax at statutory rates, net of federal income tax		(0.82	)		(4.15	)
Research and development credits		(3.39	)		(6.37	)
Other		0.56			4.27
Change in valuation allowance		24.65			27.25
Effective tax rate	0.00%			0.00%

The Company’s income tax provision was computed based on the federal statutory rate and the average state statutory rates, net of the related federal benefit.

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of the assets and liabilities for financial reporting purposes and the amounts used for income and for tax carryforwards, recorded at the enacted federal statutory income tax rate. Significant components of the Company’s deferred tax assets and liabilities are as follows:

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	24,966,019		$	19,946,123
Accrued expenses		413,048			595,209
Stock-based compensation		738,768			603,408
Research and development credits		4,640,960			3,852,714
Operating lease right-of-use assets, net		37,793			—
Other		2,423			13,276
Total deferred tax assets		30,799,011			25,010,730
Deferred tax liabilities:
Furniture and equipment		24,967			8,390
Operating lease liability		36,044			—
Total deferred tax liabilities		61,011			8,390
Net deferred tax assets before valuation allowance		30,738,000			25,002,340
Less valuation allowance		(30,738,000	)		(25,002,340	)
Net deferred tax asset	$	—		$	—

When realization of the deferred tax asset is more likely than not to occur, the benefit related to the deductible temporary differences attributable to operation is recognized as a reduction of income tax expense. Valuation allowances are provided against deferred tax assets when, based on all available evidence, it is considered more likely than not that some portion or all of the recorded deferred tax assets will not be realized in future periods. The Company cannot be certain that future taxable income will be sufficient to realize its deferred tax assets, and accordingly, a full valuation allowance has been provided on its net deferred tax assets. The valuation allowance increased $5,735,658 and $2,832,878 in 2019 and 2018, respectively, as a result of an increase in the net operating loss (“NOL”) and an increase of research and development credits carryforwards. The Company continues to monitor the need for a valuation allowance based on the profitability of its future operations.

At December 31, 2019, the Company has $84,173,000 of federal NOL carryforwards with expirations between 2032 and 2038. The Company has $28,763,332 of federal NOL carryforwards with no expiration as a result of the 2017 Tax Act. Additionally, the Company has $70,789,456 of state and local NOL carryforwards with expiration between 2020 and 2040. Finally, at December 31, 2019, the Company has $4,640,960 of federal research and development credit carryforwards that expire at various dates through 2040.

Under the provisions of the Internal Revenue Code, NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities until fully utilized. NOL and tax credit carryforwards may be subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders by more than 50% over a three-year period, as defined in Sections 382 and 383 of the Internal Revenue Code and similar state provisions. The amount of the annual limitation is determined based on the value of the Company immediately before the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has not completed a study to assess whether a change of control has occurred or whether there have been multiple changes of control since the date of the Company’s formation due to the significant complexity and cost associated with such study and that there could be additional changes in control in the future. As a result, the Company is unable to estimate the effect of these limitations, if any, on the Company’s ability to utilize NOL and tax credit carryforwards in the future. A full valuation allowance has been provided against the Company’s NOL and tax credit carryforwards and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the NOL and tax credit carryforwards and the valuation allowance.

The Company has not yet conducted a study to document whether its research activities may qualify for the research and development tax credit. Such a study may result in an adjustment to the Company’s research and development credit carryforwards; however, until a study is completed, and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company’s research and development credit and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance.

As of December 31, 2019 and 2018, the Company had no accrued uncertain tax positions or associated interest or penalties and no amounts have been recognized in the Company’s consolidated statements of operations and comprehensive loss.

The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. All years remain open and are subject to examination by federal and state taxing authorities.

Net and Comprehensive Loss Per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Net and Comprehensive Loss Per Share Attributable to Common Stockholders

9. Net and Comprehensive Loss per Share Attributable to Common Stockholders

The following table sets forth the computation of the Company’s basic and diluted net and comprehensive loss per share attributable to common stockholders for the periods presented:

	Year Ended December 31,
	2019			2018
Net and comprehensive loss attributable to common stockholders	$	(23,270,514	)	$	(10,396,635	)
Weighted average common shares used in computing net and comprehensive loss per share attributable to common stockholders, basic and diluted		40,588,004			33,930,846
Net and comprehensive loss per share attributable to common stockholders, basic and diluted	$	(0.57	)	$	(0.31	)

The following weighted average common stock equivalents were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have had an anti-dilutive effect:

	Year Ended December 31,
	2019		2018
Options to purchase common stock		5,335,850		3,351,132
Warrants to purchase common stock		917,562		317,562

Quarterly Results (Unaudited)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Data [Abstract]

Quarterly Results

10. Quarterly Results (unaudited)

The following is a summary of our unaudited quarterly results for the years ended December 31, 2019 and 2018.

	Quarter Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	(unaudited)
Total operating expenses	$	8,841,293		$	5,978,919		$	4,966,638		$	4,657,232
Loss from operations		(8,841,293	)		(5,978,919	)		(4,966,638	)		(4,657,232	)
Other income		348,468			295,303			318,708			211,089
Net and comprehensive loss attributable to common stockholders	$	(8,492,825	)	$	(5,683,616	)	$	(4,647,930	)	$	(4,446,143	)
Net and comprehensive loss per share attributable to common stockholders, basic and diluted	$	(0.21	)	$	(0.14	)	$	(0.11	)	$	(0.11	)
Weighted average number of common shares used in computing net and comprehensive loss per share:
Basic and diluted		40,588,004			40,588,004			40,588,004			40,588,004

	Quarter Ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	(unaudited)
License revenue, and other	$	—		$	1,333,333		$	18,821,953		$	2,144
Total operating expenses		7,476,648			7,369,788			7,623,916			8,868,322
(Loss) income from operations		(7,476,648	)		(6,036,455	)		11,198,037			(8,866,178	)
Other income		51,116			46,464			339,441			347,588
Net and comprehensive (loss) income attributable to common stockholders	$	(7,425,532	)	$	(5,989,991	)	$	11,537,478		$	(8,518,590	)
Net and comprehensive (loss) income per share attributable to common stockholders, basic and diluted	$	(0.27	)	$	(0.22	)	$	0.28		$	(0.21	)
Weighted average number of common shares used in computing net and comprehensive (loss) income per share:
Basic		27,045,509			27,340,914			40,527,722			40,587,928
Diluted		27,045,509			27,340,914			40,961,620			40,587,928

The sum of the quarterly net loss per share attributable to common stockholders may not equal the annual amounts reported because per share amounts are computed independently for each quarter and for full year based on respective weighted-average common shares outstanding and other dilutive potential common stockholders.

The diluted earnings per share (“EPS”) calculation for the three months ended September 30, 2018 includes the dilutive common share impact of 426,860 options to purchase common stock and 7,038 unvested restricted stock. Furthermore, the diluted EPS calculation for the three months ended September 30, 2018 excludes 2.4 million options to purchase common stock that was outstanding but unvested and the effect of weighted average common stock share equivalents of 0.1 million for options to purchase common stock and 0.3 million for warrants to purchase common stock as their effect is anti-dilutive. Holders of non-vested stock-based compensation awards do not have voting rights. Diluted and Basic weighted average number of common shares were the exact same in every other period presented within the table above.

Leases

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Leases

11. Leases

At December 31, 2019, the Company is a party to one property lease in Cincinnati, Ohio under an arrangement which provides the right to use the underlying asset and require lease payments for the lease term. During the fourth quarter of 2019, the Company terminated its leases in Lexington, Massachusetts and Dexter, Michigan; no penalties were incurred related to these terminations. The Cincinnati, Ohio lease agreement obligates the Company to pay real estate taxes, insurance and certain maintenance costs (hereinafter referred to as non-lease components). The Company’s lease arrangement contains a renewal provision of 5 years, exercisable at the Company's option. The Company’s lease agreement does not contain any material residual value guarantees or material restrictive covenants.

The Company determines if an arrangement is an operating lease at inception. Leases with an initial term of 12 months or less are not recorded on the consolidated balance sheet. All other leases are recorded on the consolidated balance sheet with a corresponding operating lease asset, net, representing the right to use the underlying asset for the lease term and the operating lease liabilities representing the obligation to make lease payments arising from the lease.

Operating lease assets and operating lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term and include options to extend or terminate the lease when they are reasonably certain to be exercised. The present value of lease payments is determined primarily using the incremental borrowing rate based on the information available at lease commencement date. Lease agreements with lease and non-lease components are generally accounted for as a single lease component. The Company’s operating lease expense is recognized on a straight-line basis over the lease term and are recorded in general and administrative expenses on the consolidated statements of operations and comprehensive loss.

The following table presents the lease cost and information related to the right-of-use assets and operating lease liabilities:

	Year Ended
	December 31, 2019
Lease cost
Average rent expense	$	242,690
Other information
Cash paid for amounts included in the measurement of operating lease liabilities	$	242,581

The weighted average remaining lease term and discount rate at December 31, 2019
Weighted-average remaining lease term - operating leases		1.58
Weighted-average discount rate - operating leases		13.28	%

As of December 31, 2019, future payments related to operating leases activities are presented in the table below:

	2020		2021		2022 and Thereafter		Total
Operating leases	$	117,781	$	69,685	$	—	$	187,466
Less interest								(17,473	)
Present value of lease liabilities							$	169,993

Employee Retirement Plan

12 Months Ended

Dec. 31, 2019

Compensation And Retirement Disclosure [Abstract]

Employee Retirement Plan

12. Employee Retirement Plan

The Company maintains a 401(k) plan (the “401k Plan”) in 2015 for the benefit of its employees. All employees who have attained the age of 21 are eligible to participate in the 401k Plan as of the first Entry Date, as defined by the 401k Plan document, following the employment date. Each employee can contribute a percentage of compensation up to a maximum of the statutory limits per year. Company contributions are discretionary. No contributions were made during 2019 or 2018.

Employee Bonus Plan

12 Months Ended

Dec. 31, 2019

Employee Bonus Plan

13. Employee Bonus Plan

The Company maintains a bonus plan for certain employees based on the achievement of certain goals and milestones. At December 31, 2019 and 2018, the Company accrued $689,830 and $1,877,455, respectively, for bonuses.

Employee Stock Purchase Plan

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee Stock Purchase Plan

14. Employee Stock Purchase Plan

In March 2017, the Board of Directors adopted and the stockholders approved the Employee Stock Purchase Plan that became effective in April 2017. On June 20, 2018, the Company’s shareholders approved the Amended and Restated 2017 Employee Stock Purchase Plan (as amended, the “ESPP”) at the Annual Meeting of Shareholders. Pursuant to the terms of the ESPP, the Company will reserve for issuance 300,000 shares of the Company’s common stock in the aggregate. Additionally, on January 1, 2019 and each January 1 thereafter through January 1, 2028, the number of shares of the Company’s common stock reserved and available for issuance under the ESPP will be cumulatively increased by the least of: (i) one percent (1%) of the number of shares of the Company’s common stock issued and outstanding on the immediately preceding December 31; (ii) 350,000 shares; or (iii) such lesser number of shares of the Company’s common stock as determined by the Board of Directors, in each case subject to adjustment in accordance with the terms of the ESPP. No shares under the ESPP are outstanding at December 31, 2019 and 2018 for the purchases made under the ESPP.

License Agreement

12 Months Ended

Dec. 31, 2019

Revenue From Contract With Customer [Abstract]

License Agreement

15. License Agreement

On June 24, 2018, the Company entered into a License Agreement (the “Gossamer License”) with Gossamer, under which the Company granted Gossamer an exclusive, sublicensable license to develop and commercialize AKB-4924 and other structurally related products worldwide, with initial development expected in the indications of induction and maintenance in ulcerative colitis and Crohn’s Disease (collectively “initial indications”). Prior to the execution of the Gossamer License, AKB-4924 was a pipeline program for the Company that recently completed a Phase 1a clinical trial in healthy volunteers.

Gossamer is responsible for the development and commercialization of the licensed products, and a joint development committee has been formed to oversee the development and manufacturing activities related to the licensed products. Under the terms of the Gossamer License, Gossamer is obligated to use its commercially reasonable efforts to develop and commercialize licensed products in the United States, two major European countries and Japan for at least one of the initial indications. The Gossamer License includes an exclusivity provision that prohibits the Company from developing, manufacturing or commercializing, and prohibits Gossamer from clinically developing or commercializing certain HIF stabilizing compounds other than as permitted in the Gossamer License. Pursuant to the terms of the Gossamer License, Gossamer made an upfront payment to the Company of $20.0 million on June 28, 2018. The $20.0 million of license revenue is recorded within the consolidated statement of operations and comprehensive loss for the year ended December 31, 2019.

The Company is also eligible to receive development, commercial and sales milestone payments, with such payments contingent on the achievement of specified milestones with respect to the first licensed product for each of the first two initial indications. The Company is also eligible to receive tiered royalties on sales of licensed products at percentages ranging from a high-single-digit to mid-teens, subject to certain customary reductions. In addition, under certain circumstances, in lieu of receiving the foregoing milestone payments and royalties, the Company may elect to receive a specified percentage of payments received by Gossamer and its stockholders (with some exclusions) in connection with Gossamer’s grant of a sublicense or other rights to the licensed products or if Gossamer undergoes a change of control and the value of the transaction exceeds a certain value (provided that Gossamer can prevent the Company from exercising this option if the parent company of Gossamer is the entity undergoing the change of control). Conversely, the Company could be required to accept such a specified percentage of those payments if Gossamer agrees to pay the Company a certain minimum upon Gossamer and its stockholders being paid. Such amount may be reduced if the subject transaction includes pharmaceutical candidates or products or other named asset categories in addition to the licensed products.

The Gossamer License expires on a licensed-product-by-licensed-product and country-by-country basis on the later of fifteen years from the date of first commercial sale or when there is no longer a valid patent claim covering such licensed product in such country. Either party may terminate the Gossamer License for an uncured material breach by the other party or upon the bankruptcy or insolvency of the other party. Gossamer may terminate the Gossamer License in the event Gossamer determines there is a potential safety or efficacy issue with the licensed products. The Company may terminate the Gossamer License if Gossamer institutes certain actions related to the licensed patents. Under certain termination circumstances, the Company would have worldwide rights to the terminated program.

As of December 31, 2019, all development milestones, sales-based milestones and royalty payments within the Gossamer License are constrained to the point where no transaction price has been allocated to the future milestones or royalty payments.

Restructuring

12 Months Ended

Dec. 31, 2019

Restructuring And Related Activities [Abstract]

Restructuring

16. Restructuring

In April 2019, the Company executed a realignment plan to reduce operating costs and better align its workforce with the needs of its ongoing business. The realignment plan reduced the Company’s workforce by 11 employees, representing approximately 41% of its workforce. As a result of this realignment plan, the Company recorded employee severance expense of $0.9 million during the year ended December 31, 2019. On October 15, 2019, the Company’s Chief Executive Officer and Chief Financial and Business Officer departed from their positions. The Chief Executive Officer also resigned as a director. In connection with these departures, the Company recorded severance expenses of $1.0 million during the year ended December 31, 2019 for employee related costs, including severance benefits and payment of healthcare insurance premiums. These amounts are included within restructuring expense in the consolidated statements of operations and comprehensive loss and are expected to be substantially paid in cash by October 31, 2020. Additionally, the Company recorded a one-time stock-based compensation cumulative reversal of $1.1 million during the year ended December 31, 2019 for the forfeitures of outstanding equity awards. Total cash payments against the severance liability was approximately $1.1 million in 2019. The remaining liability as of December 31, 2019 was approximately $0.8 million and is included in accounts payable and accrued expenses in the consolidated balance sheet.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

The Company’s consolidated financial statements are stated in U.S. dollars.

Segment Information

Use of Estimates

Cash and Cash Equivalents

Revenue Recognition

Upfront License Fees

Development Milestone Payments

Sales-based Milestone and Royalty Payments

Grant Income

Grant income is recognized as earned based on contract work performed.

Research and Development

Patents

Costs incurred in connection with the application for and issuances of patents are expensed as incurred.

Income Taxes

Net Loss and Comprehensive Loss per Share Attributable to Common Stockholders

Stock-Based Compensation

Fair Value of Financial Instruments

•

Level 1 – Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date

•

Level 2 – Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly

•

Level 3 – Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
December 31, 2019
Assets:
Cash and cash equivalents	$	38,524,536	$	—	$	—	$	38,524,536
Total assets	$	38,524,536	$	—	$	—	$	38,524,536
December 31, 2018
Assets:
Cash and cash equivalents	$	62,614,010	$	—	$	—	$	62,614,010
Total assets	$	62,614,010	$	—	$	—	$	62,614,010

Concentrations of Credit Risk and Off-Balance Sheet Risk

Comprehensive Loss

Furniture and Equipment

Leases

Recent Accounting Pronouncements

No other new accounting pronouncement recently issued or newly effective had or is expected to have a material impact on the Company’s consolidated financial statements.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Assets Measured on Recurring Basis

The assets of the Company measured at fair value on a recurring basis as of December 31, 2019 and 2018 are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
December 31, 2019
Assets:
Cash and cash equivalents	$	38,524,536	$	—	$	—	$	38,524,536
Total assets	$	38,524,536	$	—	$	—	$	38,524,536
December 31, 2018
Assets:
Cash and cash equivalents	$	62,614,010	$	—	$	—	$	62,614,010
Total assets	$	62,614,010	$	—	$	—	$	62,614,010

Accounts Payable and Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2019

Payables And Accruals [Abstract]

Schedule of Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consist of the following as of:

	December 31,
	2019		2018
Accounts payable	$	439,785	$	595,680
Restructuring accrual (see Note 16)		793,913		—
Professional fees		346,999		487,923
Accrued bonus		689,830		1,877,455
Accrued retention bonus		521,859		—
Accrued vacation		43,470		90,663
Accrued project costs		382,131		2,232,014
Other		13,463		173,182
Total accounts payable and accrued expenses	$	3,231,450	$	5,456,917

Furniture and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Summary of Components of Furniture and Equipment

Furniture and equipment consist of the following as of:

	December 31,
	2019			2018
Furniture	$	154,669		$	156,928
Computers		56,443			75,716
Equipment		246,056			141,067
Leasehold improvements		35,869			35,869
Total furniture and equipment		493,037			409,580
Accumulated depreciation		(328,850	)		(311,131	)
Furniture and equipment, net	$	164,187		$	98,449

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes the stock option activity during the years ended December 31, 2019 and 2018:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding, January 1, 2018		1,912,980		$	3.72		8.24	$	2,738,704
Granted		1,615,200			3.64
Exercised		(52,099	)		1.47
Expired/cancelled		(124,949	)		3.23
Outstanding, December 31, 2018		3,351,132		$	3.73		8.24	$	142,788
Expected to vest, December 31, 2018		2,197,619		$	4.17		9.19	$	-
Options exercisable, December 31, 2018		1,153,513		$	2.90		6.37	$	142,788
Outstanding, January 1, 2019		3,351,132		$	3.73		8.24	$	142,788
Granted		4,666,728			1.85
Exercised		—
Expired/cancelled		(2,682,010	)		2.70
Outstanding, December 31, 2019		5,335,850		$	2.60		6.23	$	2,866
Expected to vest, December 31, 2019		2,395,265		$	1.93		9.00	$	2,866
Options exercisable, December 31, 2019		2,940,585		$	3.15		3.98	$	—

Stock Options Valuation Assumptions

The calculation was based on the following assumptions.

	Year Ended December 31,
	2019			2018
Expected term (years)	5.36			6.07
Risk-free interest rate		2.24	%		2.85	%
Expected volatility		64.88	%		65.99	%
Expected dividend yield		—			—

Summary of Restricted Stock Activity

A summary of the Company’s restricted stock activity and related information for the years ended December 31, 2019 and 2018 is as follows:

	Shares			Weighted Average Grant Date Fair Value
Nonvested, January 1, 2018		91,576		$	2.12
Granted		60,000			4.75
Vested		(149,243	)		3.18
Forfeited		(2,333	)		2.25
Nonvested, December 31, 2018		—		$	—

Nonvested, January 1, 2019		—		$	—
Granted		—			—
Vested		—			—
Forfeited		—			—
Nonvested, December 31, 2019		—		$	—

Summary of Recognized Compensation Cost Related to Employee and Non-employee Stock-Based Compensation Activity

The Company recognized the following compensation cost related to employee and non-employee stock-based compensation activity for the periods presented below.

	Year Ended December 31,
	2019		2018
Research and development	$	510,923	$	392,470
General and administrative		574,919		3,039,392
Total	$	1,085,842	$	3,431,862

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Statutory Federal Income Tax

A reconciliation of the statutory federal income tax with the provision for income taxes are as follows:

	Year Ended December 31,
	2019			2018
Federal tax at statutory rate	(21.00%)			(21.00%)
State and local tax at statutory rates, net of federal income tax		(0.82	)		(4.15	)
Research and development credits		(3.39	)		(6.37	)
Other		0.56			4.27
Change in valuation allowance		24.65			27.25
Effective tax rate	0.00%			0.00%

Schedule of Significant Components of Deferred Tax Assets and Liabilities

Significant components of the Company’s deferred tax assets and liabilities are as follows:

	December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards	$	24,966,019		$	19,946,123
Accrued expenses		413,048			595,209
Stock-based compensation		738,768			603,408
Research and development credits		4,640,960			3,852,714
Operating lease right-of-use assets, net		37,793			—
Other		2,423			13,276
Total deferred tax assets		30,799,011			25,010,730
Deferred tax liabilities:
Furniture and equipment		24,967			8,390
Operating lease liability		36,044			—
Total deferred tax liabilities		61,011			8,390
Net deferred tax assets before valuation allowance		30,738,000			25,002,340
Less valuation allowance		(30,738,000	)		(25,002,340	)
Net deferred tax asset	$	—		$	—

Net and Comprehensive Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net and Comprehensive Loss per Share

The following table sets forth the computation of the Company’s basic and diluted net and comprehensive loss per share attributable to common stockholders for the periods presented:

	Year Ended December 31,
	2019			2018
Net and comprehensive loss attributable to common stockholders	$	(23,270,514	)	$	(10,396,635	)
Weighted average common shares used in computing net and comprehensive loss per share attributable to common stockholders, basic and diluted		40,588,004			33,930,846
Net and comprehensive loss per share attributable to common stockholders, basic and diluted	$	(0.57	)	$	(0.31	)

Schedule of Weighted Average Common Stock Equivalents Excluded from Calculation of Diluted Net Loss per Share

	Year Ended December 31,
	2019		2018
Options to purchase common stock		5,335,850		3,351,132
Warrants to purchase common stock		917,562		317,562

Quarterly Results (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Summary of Quarterly Results

The following is a summary of our unaudited quarterly results for the years ended December 31, 2019 and 2018.

	Quarter Ended
	March 31, 2019			June 30, 2019			September 30, 2019			December 31, 2019
	(unaudited)
Total operating expenses	$	8,841,293		$	5,978,919		$	4,966,638		$	4,657,232
Loss from operations		(8,841,293	)		(5,978,919	)		(4,966,638	)		(4,657,232	)
Other income		348,468			295,303			318,708			211,089
Net and comprehensive loss attributable to common stockholders	$	(8,492,825	)	$	(5,683,616	)	$	(4,647,930	)	$	(4,446,143	)
Net and comprehensive loss per share attributable to common stockholders, basic and diluted	$	(0.21	)	$	(0.14	)	$	(0.11	)	$	(0.11	)
Weighted average number of common shares used in computing net and comprehensive loss per share:
Basic and diluted		40,588,004			40,588,004			40,588,004			40,588,004

	Quarter Ended
	March 31, 2018			June 30, 2018			September 30, 2018			December 31, 2018
	(unaudited)
License revenue, and other	$	—		$	1,333,333		$	18,821,953		$	2,144
Total operating expenses		7,476,648			7,369,788			7,623,916			8,868,322
(Loss) income from operations		(7,476,648	)		(6,036,455	)		11,198,037			(8,866,178	)
Other income		51,116			46,464			339,441			347,588
Net and comprehensive (loss) income attributable to common stockholders	$	(7,425,532	)	$	(5,989,991	)	$	11,537,478		$	(8,518,590	)
Net and comprehensive (loss) income per share attributable to common stockholders, basic and diluted	$	(0.27	)	$	(0.22	)	$	0.28		$	(0.21	)
Weighted average number of common shares used in computing net and comprehensive (loss) income per share:
Basic		27,045,509			27,340,914			40,527,722			40,587,928
Diluted		27,045,509			27,340,914			40,961,620			40,587,928

Leases (Tables)

12 Months Ended

Dec. 31, 2019

Leases [Abstract]

Summary of Lease Cost and Information Related to the Right-of-Use Assets and Operating Lease Liabilities

The following table presents the lease cost and information related to the right-of-use assets and operating lease liabilities:

	Year Ended
	December 31, 2019
Lease cost
Average rent expense	$	242,690
Other information
Cash paid for amounts included in the measurement of operating lease liabilities	$	242,581

The weighted average remaining lease term and discount rate at December 31, 2019
Weighted-average remaining lease term - operating leases		1.58
Weighted-average discount rate - operating leases		13.28	%

Schedule of Future Payments Related to Operating Leases Activities

As of December 31, 2019, future payments related to operating leases activities are presented in the table below:

	2020		2021		2022 and Thereafter		Total
Operating leases	$	117,781	$	69,685	$	—	$	187,466
Less interest								(17,473	)
Present value of lease liabilities							$	169,993

Nature of Organization and Operations - Additional Information (Detail) - USD ($)			12 Months Ended
	Jul. 02, 2018	Jun. 28, 2018	Dec. 31, 2018	Dec. 31, 2019
Class Of Stock [Line Items]
Underwriting discounts and commissions and offering expenses paid			$ 3,502,543
Proceeds from sale of common stock			51,621,570
Cash and cash equivalents			$ 62,614,010	$ 38,524,536
2018 Public Offering [Member]
Class Of Stock [Line Items]
Common stock sold in offering		11,688,000
Underwriting discounts and commissions and offering expenses paid	$ 3,500,000
Proceeds from sale of common stock	$ 48,100,000
Underwriters' Exercise of Option [Member]
Class Of Stock [Line Items]
Common stock sold in offering	1,720,200

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Segment	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment \| Segment	1
Uncertain tax positions	$ 0		$ 0
ASU 2018-07 [Member]
Summary Of Significant Accounting Policies [Line Items]
One-time cumulative adjustment upon adoption		$ 5,717
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Furniture and equipment estimated useful lives	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Furniture and equipment estimated useful lives	7 years
Certificates of Deposits [Member]
Summary Of Significant Accounting Policies [Line Items]
Short-term investments	$ 100,000

Summary of Significant Accounting Policies - Schedule of Assets Measured on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 38,524,536	$ 62,614,010
Total assets	38,524,536	62,614,010
Level 1 [Member]
Assets:
Cash and cash equivalents	38,524,536	62,614,010
Total assets	$ 38,524,536	$ 62,614,010

Accounts Payable and Accrued Expenses - Schedule of Accounts Payable and Accrued Expenses (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 439,785	$ 595,680
Restructuring accrual (see Note 16)	793,913
Professional fees	346,999	487,923
Accrued bonus	689,830	1,877,455
Accrued retention bonus	521,859
Accrued vacation	43,470	90,663
Accrued project costs	382,131	2,232,014
Other	13,463	173,182
Total accounts payable and accrued expenses	$ 3,231,450	$ 5,456,917

Furniture and Equipment - Summary of Components of Furniture and Equipment (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Furniture and equipment	$ 493,037	$ 409,580
Accumulated depreciation	(328,850)	(311,131)
Furniture and equipment, net	164,187	98,449
Furniture [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	154,669	156,928
Computers [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	56,443	75,716
Equipment [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	246,056	141,067
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Furniture and equipment	$ 35,869	$ 35,869

Common Stock - Additional Information (Detail) - USD ($)		12 Months Ended
	Oct. 14, 2019	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized		300,000,000	300,000,000
Common stock, par value		$ 0.0001	$ 0.0001
Dividends common stock declared or paid		$ 0
Warrants outstanding		917,562	317,562
Number of warrants issued to purchase common stock	600,000	317,562	317,562
Warrants exercise price per share	$ 0.486		$ 5.00
Warrants term			3 years
Warrants vesting period	6 months
Warrants expiration date		Oct. 24, 2024	Mar. 15, 2020

Preferred Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity Disclosure [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	May 31, 2019	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020	Jan. 01, 2019	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options to purchase common stock, granted				4,666,728	1,615,200
Aggregate intrinsic value of option outstanding			$ 2,866	$ 2,866	$ 142,788			$ 2,738,704
Stock options exercised				0	52,099
Stock options exercised, intrinsic value					$ 139,108
Unrecognized compensation cost related to stock options			$ 2,309,337	$ 2,309,337
Weighted-average fair value of options granted			$ 1.11	$ 1.11	$ 2.22
Chief Executive Officer and Chief Financial and Business Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
One-time stock-based compensation cumulative reversal for forfeitures of outstanding equity awards			$ 1,051,735	$ 1,100,000
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period				48 months
Compensation expense				$ 1,085,842	$ 2,982,173
Weighted average period expected to be recognized				2 years 3 months 21 days
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense				$ 0	$ 449,689
2017 Stock Option and Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares available for issuance		4,600,000					1,623,520
Percentage applied to the outstanding shares as annual increase in number of shares authorized for issuance		4.00%
2017 Stock Option and Incentive Plan [Member] \| Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares available for issuance			1,983,093	1,983,093	2,959,562
Term of options to be granted				10 years
Options to purchase common stock, granted				4,666,728	1,615,200
Shares issued for special retention grant	2,419,050
2017 Stock Option and Incentive Plan [Member] \| Stock Option [Member] \| One-year Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage				25.00%
2017 Stock Option and Incentive Plan [Member] \| Stock Option [Member] \| First Installment [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage	50.00%
Option, vesting date	Jun. 30, 2020
2017 Stock Option and Incentive Plan [Member] \| Stock Option [Member] \| Second Installment [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage	50.00%
Option, vesting date	Jun. 30, 2021
2017 Stock Option and Incentive Plan [Member] \| Subsequent Event [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares available for issuance						1,623,520

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding at beginning balance	3,351,132	1,912,980
Shares, Granted	4,666,728	1,615,200
Shares, Exercised	0	(52,099)
Shares, Expired/cancelled	(2,682,010)	(124,949)
Shares, Outstanding at ending balance	5,335,850	3,351,132	1,912,980
Shares, Expected to vest	2,395,265	2,197,619
Shares, Options exercisable	2,940,585	1,153,513
Weighted Average Exercise Price, Outstanding at beginning balance	$ 3.73	$ 3.72
Weighted Average Exercise Price, Granted	1.85	3.64
Weighted Average Exercise Price, Exercised		1.47
Weighted Average Exercise Price, Expired/cancelled	2.70	3.23
Weighted Average Exercise Price, Outstanding at ending balance	2.60	3.73	$ 3.72
Weighted Average Exercise Price, Expected to vest	1.93	4.17
Weighted Average Exercise Price, Options exercisable	$ 3.15	$ 2.90
Weighted Average Remaining Contractual Term, Outstanding	6 years 2 months 23 days	8 years 2 months 26 days	8 years 2 months 26 days
Weighted Average Remaining Contractual Term, Expected to vest	9 years	9 years 2 months 8 days
Weighted Average Remaining Contractual Term, Options exercisable	3 years 11 months 23 days	6 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding	$ 2,866	$ 142,788	$ 2,738,704
Aggregate Intrinsic Value, Expected to vest	$ 2,866
Aggregate Intrinsic Value, Options exercisable		$ 142,788

Stock-Based Compensation - Stock Options Valuation Assumptions (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (years)	5 years 4 months 9 days	6 years 25 days
Risk-free interest rate	2.24%	2.85%
Expected volatility	64.88%	65.99%

Stock-Based Compensation - Summary of Restricted Stock Activity (Detail) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Nonvested beginning balance \| shares	91,576
Shares, Granted \| shares	60,000
Shares, Vested \| shares	(149,243)
Shares, Forfeited \| shares	(2,333)
Weighted Average Grant Date Fair Value, Nonvested beginning balance \| $ / shares	$ 2.12
Weighted Average Grant Date Fair Value, Granted \| $ / shares	4.75
Weighted Average Grant Date Fair Value, Vested \| $ / shares	3.18
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	$ 2.25

Stock-Based Compensation - Summary of Recognized Compensation Cost Related to Employee and Non-employee Stock-Based Compensation Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,085,842	$ 3,431,862
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	510,923	392,470
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 574,919	$ 3,039,392

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Line Items]
Current income tax expense or benefit	$ 0	$ 0
Deferred income tax expense or benefit	0	0
Increase in valuation allowance	5,735,658	2,832,878
Accrued uncertain tax positions	0	0
Accrued interest and penalties on uncertain tax positions	0	$ 0
Federal [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	84,173,000
2017 Tax Act, net operating loss carryforwards	28,763,332
State [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 70,789,456
Maximum [Member] \| Federal [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2038
Maximum [Member] \| State [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2040
Minimum [Member] \| Federal [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2032
Minimum [Member] \| State [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards, expiration date	Dec. 31, 2020
Research and Development [Member] \| Federal [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 4,640,960
Tax credit carryforwards, expiration date	Dec. 31, 2040

Income Taxes - Schedule of Reconciliation of Statutory Federal Income Tax (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal tax at statutory rate	(21.00%)	(21.00%)
State and local tax at statutory rates, net of federal income tax	(0.82%)	(4.15%)
Research and development credits	(3.39%)	(6.37%)
Other	0.56%	4.27%
Change in valuation allowance	24.65%	27.25%
Effective tax rate	0.00%	0.00%

Income Taxes - Schedule of Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 24,966,019	$ 19,946,123
Accrued expenses	413,048	595,209
Stock-based compensation	738,768	603,408
Research and development credits	4,640,960	3,852,714
Operating lease right-of-use assets, net	37,793
Other	2,423	13,276
Total deferred tax assets	30,799,011	25,010,730
Deferred tax liabilities:
Furniture and equipment	24,967	8,390
Operating lease liability	36,044
Total deferred tax liabilities	61,011	8,390
Net deferred tax assets before valuation allowance	30,738,000	25,002,340
Less valuation allowance	$ (30,738,000)	$ (25,002,340)

Net and Comprehensive Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net and Comprehensive Loss per Share (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net and comprehensive loss attributable to common stockholders	$ (4,446,143)	$ (4,647,930)	$ (5,683,616)	$ (8,492,825)	$ (8,518,590)	$ 11,537,478	$ (5,989,991)	$ (7,425,532)	$ (23,270,514)	$ (10,396,635)
Weighted average common shares used in computing net and comprehensive loss per share attributable to common stockholders, basic and diluted	40,588,004	40,588,004	40,588,004	40,588,004					40,588,004	33,930,846
Net and comprehensive loss per share attributable to common stockholders, basic and diluted	$ (0.11)	$ (0.11)	$ (0.14)	$ (0.21)	$ (0.21)	$ 0.28	$ (0.22)	$ (0.27)	$ (0.57)	$ (0.31)

Net and Comprehensive Loss Per Share Attributable to Common Stockholders - Schedule of Weighted Average Common Stock Equivalents Excluded from Calculation of Diluted Net Loss per Share (Detail) - shares	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	2,400,000
Options to Purchase Common Stock [Member] \| Weighted Average [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	100,000	5,335,850	3,351,132
Warrants to Purchase Common Stock [Member] \| Weighted Average [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	300,000	917,562	317,562

Quarterly Results (unaudited) - Summary of Unaudited Quarterly Results (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
License revenue, and other					$ 2,144	$ 18,821,953	$ 1,333,333			$ 20,157,430
Type of Revenue [Extensible List]					arpo:LicenseRevenueAndOtherMember	arpo:LicenseRevenueAndOtherMember	arpo:LicenseRevenueAndOtherMember	arpo:LicenseRevenueAndOtherMember		arpo:LicenseRevenueAndOtherMember
Total operating expenses	$ 4,657,232	$ 4,966,638	$ 5,978,919	$ 8,841,293	$ 8,868,322	$ 7,623,916	$ 7,369,788	$ 7,476,648	$ 24,444,082	$ 31,338,674
Loss from operations	(4,657,232)	(4,966,638)	(5,978,919)	(8,841,293)	(8,866,178)	11,198,037	(6,036,455)	(7,476,648)	(24,444,082)	(11,181,244)
Other income	211,089	318,708	295,303	348,468	347,588	339,441	46,464	51,116	1,173,568	784,609
Net and comprehensive (loss) income attributable to common stockholders	$ (4,446,143)	$ (4,647,930)	$ (5,683,616)	$ (8,492,825)	$ (8,518,590)	$ 11,537,478	$ (5,989,991)	$ (7,425,532)	$ (23,270,514)	$ (10,396,635)
Basic and diluted	$ (0.11)	$ (0.11)	$ (0.14)	$ (0.21)	$ (0.21)	$ 0.28	$ (0.22)	$ (0.27)	$ (0.57)	$ (0.31)
Weighted average number of common shares used in computing net and comprehensive (loss) income per share:
Basic					40,587,928	40,527,722	27,340,914	27,045,509
Diluted					40,587,928	40,961,620	27,340,914	27,045,509
Basic and diluted	40,588,004	40,588,004	40,588,004	40,588,004					40,588,004	33,930,846

Quarterly Results (unaudited) - Additional Information (Detail) - shares	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive impact of options to purchase common shares	426,860
Number of anti-dilutive securities excluded from computation of earnings per share	2,400,000
Restricted Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive impact of options to purchase common shares	7,038
Weighted Average [Member] \| Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Number of anti-dilutive securities excluded from computation of earnings per share	100,000	5,335,850	3,351,132
Weighted Average [Member] \| Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Number of anti-dilutive securities excluded from computation of earnings per share	300,000	917,562	317,562

Leases - Additional Information (Detail)	3 Months Ended
Leases - Additional Information (Detail)	Dec. 31, 2019 USD ($)
Leases [Abstract]
Penalties incurred on termination of leases	$ 0
Lease arrangement, renewal term	5 years

Leases - Summary of Lease Cost and Information Related to the Right-of-Use Assets and Operating Lease Liabilities (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease cost
Average rent expense	$ 242,690
Other information
Cash paid for amounts included in the measurement of operating lease liabilities	$ 242,581
The weighted average remaining lease term and discount rate
Weighted-average remaining lease term - operating leases	1 year 6 months 29 days
Weighted-average discount rate - operating leases	13.28%

Leases - Schedule of Future Payments Related to Operating Leases Activities (Detail)	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating leases, 2020	$ 117,781
Operating leases, 2021	69,685
Total Lease Payments	187,466
Less interest	(17,473)
Present value of lease liabilities	$ 169,993

Employee Retirement Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Contributions made under Plan	$ 0	$ 0
Defined contribution plan, sponsor location [extensible list]	country:US	country:US
Defined contribution plan, tax status [extensible list]	us-gaap:QualifiedPlanMember	us-gaap:QualifiedPlanMember

Employee Bonus Plan - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred Compensation Arrangements [Abstract]
Accrued bonus	$ 689,830	$ 1,877,455

Employee Stock Purchase Plan - Additional Information (Detail) - shares	Jun. 20, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding		5,335,850	3,351,132	1,912,980
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding		0	0
Common Stock [Member] \| Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares available for issuance	300,000
Maximum number of shares provided for issuance	350,000
Percentage of annual increase in number of shares reserved for issuance	1.00%

License Agreement - Additional Information (Detail) - USD ($)		3 Months Ended			12 Months Ended
	Jun. 28, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
License Agreement [Line Items]
Cash received from license agreement	$ 20,000,000
License revenue		$ 2,144	$ 18,821,953	$ 1,333,333		$ 20,157,430
License [Member]
License Agreement [Line Items]
License revenue					$ 20,000,000

Restructuring - Additional Information (Detail)	1 Months Ended	3 Months Ended	12 Months Ended
Restructuring - Additional Information (Detail)	Apr. 30, 2019 Employee	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Oct. 15, 2019 USD ($)
Restructuring Cost And Reserve [Line Items]
Remaining liability related to severance		$ 793,913	$ 793,913
Chief Executive Officer and Chief Financial and Business Officer [Member]
Restructuring Cost And Reserve [Line Items]
One-time stock-based compensation cumulative reversal for forfeitures of outstanding equity awards		1,051,735	1,100,000
Accounts Payable and Accrued Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Remaining liability related to severance		$ 800,000	800,000
Workforce Reduction [Member]
Restructuring Cost And Reserve [Line Items]
Realignment plan, number of current workforce reduced \| Employee	11
Realignment plan, number of workforce reduced, period percent	41.00%
Realignment plan, employee severance expense			900,000
Estimated employee related costs				$ 1,000,000
Cash payments against severance liability			$ 1,100,000