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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2017	Aug. 10, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Trading Symbol	ARPO
Entity Filer Category	Smaller Reporting Company
Entity Registrant Name	Aerpio Pharmaceuticals, Inc.
Entity Central Index Key	0001422142
Entity Common Stock, Shares Outstanding		27,070,038

Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 28,847,937	$ 1,609,694
Short-term investments	50,000	50,000
Accounts receivable	4,264	4,157
Prepaid research and development contracts	311,064	353,434
Other current assets	431,151	209,038
Total current assets	29,644,416	2,226,323
Furniture and equipment, net	129,026	149,595
Deposits	20,960	20,960
Total assets	29,794,402	2,396,878
Current liabilities:
Accounts payable and accrued expenses	1,856,817	2,470,970
Convertible notes		12,386,647
Total current liabilities	1,856,817	14,857,617
Commitments and contingencies (Note 11)
Redeemable convertible preferred stock (all classes)		73,757,890
Stockholders’ equity (deficit):
Common stock, $0.0001 par value per share; 300,000,000 and 17,440,436 shares authorized and 27,070,038 and 1,240,925 shares issued and outstanding at June 30, 2017 and December 31, 2016 respectively.	2,707	124
Additional paid-in capital	125,612,938
Accumulated deficit	(97,678,060)	(86,218,753)
Total stockholders’ equity (deficit)	27,937,585	(86,218,629)
Total liabilities, redeemable convertible preferred stock, and stockholders’ equity (deficit)	$ 29,794,402	$ 2,396,878

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	17,440,436
Common stock, shares issued	27,070,038	1,240,925
Common stock, shares outstanding	27,070,038	1,240,925

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating expenses:
Research and development	$ 3,169,115	$ 2,903,564	$ 5,424,699	$ 5,893,122
General and administrative	2,414,747	1,473,869	4,918,748	2,689,754
Total operating expenses	5,583,862	4,377,433	10,343,447	8,582,876
Loss from operations	(5,583,862)	(4,377,433)	(10,343,447)	(8,582,876)
Grant income	11,239	80,954	46,896	89,624
Interest income (expense), net	52,316	(88,783)	(219,459)	(87,706)
Other income, net				997
Total other income (expense)	63,555	(7,829)	(172,563)	2,915
Net loss and comprehensive loss	(5,520,307)	(4,385,262)	(10,516,010)	(8,579,961)
Reconciliation to net loss attributable to common stockholders:
Net loss and comprehensive loss	(5,520,307)	(4,385,262)	(10,516,010)	(8,579,961)
Extinguishment of preferred stock		224,224		224,224
Accretion of preferred stock to redemption value		(1,028,121)	(943,297)	(2,043,492)
Net Loss attributable to common stockholders	$ (5,520,307)	$ (5,189,159)	$ (11,459,307)	$ (10,399,229)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.21)	$ (6.30)	$ (0.70)	$ (13.33)
Weighted average number of common shares used in computing net loss per share attributable to common stockholders, basic and diluted	26,895,164	823,097	16,313,324	780,152

Condensed Consolidated Statements of Stockholders Equity (Deficit) - 6 months ended Jun. 30, 2017 - USD ($)	Total	Common Stock	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock, Balance at Dec. 31, 2016	$ 73,757,890				$ 73,757,890
Redeemable convertible preferred stock, Balance, Shares at Dec. 31, 2016					14,015,016
Balance at Dec. 31, 2016	(86,218,629)	$ 124		$ (86,218,753)
Balance, Shares at Dec. 31, 2016		1,240,925
Redeemable convertible preferred stock, Adjustment of redeemable convertible preferred stock to redemption value					$ 943,297
Adjustment of redeemable convertible preferred stock to redemption value	(943,297)			(943,297)
Redeemable convertible preferred stock, Conversion of preferred stock					$ (74,701,187)
Redeemable convertible preferred stock, Conversion of preferred stock, Shares					(14,015,016)
Conversion of preferred stock	74,701,187	$ 1,402	$ 74,699,785
Conversion of preferred stock, Shares		14,015,016
Conversion of convertible notes and accrued interest	13,447,934	$ 274	13,447,660
Conversion of convertible notes and accrued interest, Shares		2,744,059
Share exchange in connection with Merger		$ 100	(100)
Share exchange in connection with Merger, Shares		1,000,000
Issuance of common stock, net of issuance costs	37,163,390	$ 805	37,162,585
Issuance of common stock, net of issuance costs, Shares		8,049,555
Issuance of common stock upon exercise of stock options	$ 36,101	$ 3	36,098
Issuance of common stock upon exercise of stock options, Shares	25,729	25,729
Forfeiture of restricted stock		$ (1)	1
Forfeiture of restricted stock, Shares		(5,246)
Share-based compensation expense	$ 266,909		266,909
Net loss	(10,516,010)			(10,516,010)
Balance at Jun. 30, 2017	$ 27,937,585	$ 2,707	$ 125,612,938	$ (97,678,060)
Balance, Shares at Jun. 30, 2017		27,070,038

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities:
Net loss	$ (10,516,010)	$ (8,579,961)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	27,117	37,991
Stock-based compensation	266,909	244,765
Amortization of debt issuance costs	75,561	59,277
Interest expense related to convertible note conversion	204,929	89,962
Changes in operating assets and liabilities:
Accounts receivable	(107)	113,943
Prepaid expenses and current other assets	(179,743)	259,938
Accounts payable and other current liabilities	(130,711)	(71,261)
Net cash used in operating activities	(10,252,055)	(7,845,346)
Investing activities:
Purchase of furniture and equipment	(6,547)	(113,297)
Net cash used in investing activities	(6,547)	(113,297)
Financing activities:
Proceeds from exercise of stock options	36,101	18,969
Proceeds from issuances of convertible notes	297,354	4,536,531
Cash paid for debt issuance costs		(138,312)
Proceeds from sale of common stock	40,247,775
Cash paid in connection with the sale of common stock	(3,084,385)
Net cash provided by financing activities	37,496,845	4,417,188
Net increase (decrease) in cash and cash equivalents	27,238,243	(3,541,455)
Cash and cash equivalents at beginning of year	1,609,694	5,144,211
Cash and cash equivalents, six months ended	28,847,937	1,602,756
Non-cash financing activities
Conversion of preferred stock into common stock	74,701,187
Conversion of notes and accrued interest into common stock	13,447,934
Accretion of preferred stock to redemption value	$ 943,297	2,043,492
Extinguishment of preferred stock		$ (224,224)

Nature of Organization and Operations	6 Months Ended
Nature of Organization and Operations	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Organization and Operations	1. Nature of Organization and Operations Aerpio Pharmaceuticals, Inc. (the “Company”) was incorporated as Zeta Acquisition Corp. II (“Zeta”) in the State of Delaware on November 16, 2007. Prior to the Merger, (as defined below), Zeta was a “shell company” (as defined in Rule 12b-2 of the Securities Exchange Act of 1934, as amended). On March 3, 2017, the Company’s Board of Directors, and on March 10, 2017, the Company’s pre-Merger (as defined below) stockholders, approved an amended and restated certificate of incorporation, which, among other things, increased authorized capital stock from 100,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share, to 300,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share. On March 15, 2017, Zeta changed its name to Aerpio Pharmaceuticals, Inc. and its wholly-owned subsidiary, Aerpio Acquisition Corp., a corporation formed in the State of Delaware on March 3, 2017, merged with and into Aerpio Therapeutics, Inc., (“Aerpio”), (the “Merger”), a corporation incorporated on November 17, 2011 in the State of Delaware. Pursuant to the Merger, Aerpio remained as the surviving corporation and became the Company’s wholly-owned subsidiary. At the effective time of the Merger, the shares of the Aerpio’s (i) common stock issued and outstanding immediately prior to the closing of the Merger (including restricted common stock, whether vested or unvested, issued under the Aerpio’s 2011 Equity Incentive Plan), and (ii) redeemable convertible preferred stock issued and outstanding immediately prior to the closing of the Merger, were converted into shares of the Company’s common stock. In addition, immediately prior to the Merger, the outstanding amounts under certain Senior Secured Convertible Promissory Notes issued by Aerpio to its pre-Merger noteholders were converted into shares of Aerpio’s preferred stock, which were then converted to shares of Aerpio’s common stock and subsequently were converted into shares of the Company’s common stock, together with the other shares of the Aerpio’s common stock described above. In addition, pursuant to the Merger Agreement options to purchase shares of the Aerpio’s common stock issued and outstanding immediately prior to the closing of the Merger were assumed and converted into options to purchase shares of the Company’s common stock. All the outstanding capital stock of Aerpio was converted into shares of the Company’s common stock on a 2.3336572:1 basis. As a result of the Merger, the Company acquired the business of Aerpio and will continue the existing business operations of Aerpio as a public reporting company under the name Aerpio Pharmaceuticals, Inc. Immediately after the Merger, on March 15, 2017, Aerpio converted into a Delaware limited liability company (the “Conversion”). Immediately following the Conversion, the pre-Merger stockholders of Zeta surrendered for cancellation 4,000,000 of the 5,000,000 shares of the outstanding common stock of Zeta, (the “Share Cancellation”). Following the Share Cancellation, on March 15, 2017, the Company closed a private placement offering (the “Offering”) of 8,049,555 shares of the Company’s common stock, at a purchase price of $5.00 per share, for net proceeds of approximately $37.2 million and the issuance of warrants with a term of three years, to purchase 317,562 shares of the Company’s common stock at an exercise price of $5.00 per share. The Merger was treated as a recapitalization and reverse acquisition for financial reporting purposes. The Company is the legal acquirer of Aerpio in the transaction. However, Aerpio is considered the acquiring company for accounting purposes since (i) former Aerpio stockholders own in excess of 50% of the combined enterprise on a fully diluted basis immediately following the Merger and Offering, and (ii) all members of the Company’s executive management and Board of Directors are from Aerpio. In accordance with “reverse merger” or “reverse acquisition” accounting treatment, the unaudited condensed consolidated interim financial statements for the period ended June 30, 2017 include the accounts of the Company and its wholly owned subsidiary, Aerpio Therapeutics, LLC. The comparative historical financial statements for periods ended prior to the date of the Merger are the historical financial statements of Aerpio. Consequently, the assets and liabilities and the historical operations that are reflected in these condensed consolidated financial statements of the company are those of Aerpio, which were recorded at their historical cost basis. Unless otherwise indicated, all share and per share figures reflect the exchange of each 2.3336572 shares of Aerpio capital stock, convertible notes and share based awards, then outstanding, for 1 share of the Company’s common stock at the effective time of the Merger. The Company is a biopharmaceutical company focused on advancing first-in-class treatments for ocular disease. The Company’s lead product candidate, AKB-9778, a small molecule activator of the tie-2 pathway, is being developed for the treatment of diabetic retinopathy (“DR”). Tie-2 signaling is essential for regulating blood vessel development and the stability of mature vessels. The Company has completed a Phase 2a clinical trial in diabetic macular edema (“DME”), a swelling of the retina that is a common cause of vision loss in patients with DR and during the second quarter of 2017, initiated a twelve month, double blind Phase 2b clinical trial in patients with DR who have not developed more serious complications such as DME or proliferative diabetic retinopathy. In addition, the Company has two pipeline programs. AKB-4924 is a drug candidate for the treatment of inflammatory bowel disease and ARP-1536, humanized monoclonal antibody is a drug candidate for ocular disease. Humanized antibodies are antibodies from non-human species whose protein sequences have been modified to increase their similarity to antibodies produced naturally in humans. The Company completed a Phase 1a clinical trial in healthy volunteers for AKB-4924 and APR-1536 is currently in preclinical development. Further development on the pipeline programs is subject to receiving additional funding, which the Company may seek through collaborations with potential strategic and commercial partners. 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 has not generated any revenues to date, nor is there any assurance of any future revenues. 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.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The unaudited condensed 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 generally accepted accounting principles in the United States ("U.S. GAAP" or "GAAP") for interim financial reporting, and, in the opinion of management include all adjustments necessary for a fair presentation of the results of operations, financial position and cash flows for each period presented. All adjustments are of a normal and recurring nature. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements of Aerpio Therapeutics Inc. and related footnotes for the year ended December 31, 2016, included in the Company’s Registration Statement on Form S-1 filed with the SEC. The results of operations for the interim periods are not necessarily indicative of results of operations for a full year. The Company’s condensed 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’s sole operating segment are located in the United States of America.

Use of Estimates

The preparation of 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 financial statements and the reported amounts of revenues 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: fair value of the Company’s common stock and other equity instruments, accrued expenses, and income taxes.

The Company utilizes significant estimates and assumptions in determining the fair value of its common stock and other equity instruments. The Company granted stock options at exercise prices not less than the fair value of its common stock, as determined by the Board of Directors contemporaneously at the date such grants were made. The Board of Directors has determined the estimated fair value of the Company’s common stock based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the prices at which the Company sold shares of common and preferred stock, the superior rights and preferences of securities senior to the Company’s common stock at the time, and, for periods prior to the Offering, the likelihood of achieving a liquidity event, such as a public offering or sale of the Company.

Historically, the Company utilized various valuation methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its common stock. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions, the prices at which the Company sold shares of redeemable convertible preferred stock, the superior rights and preferences of securities senior to the Company’s common stock at the time, and, at December 31, 2016, a probability analysis of various liquidity events under differing scenarios, including both a potential public trading scenario and potential sale scenario. Significant changes to the key assumptions used in the valuations could result in different fair values of common stock and other equity instruments at each valuation date.

The Company’s results can also be affected by economic, political, legislative, regulatory, and legal actions. Economic conditions, such as recessionary trends, inflation, interest and monetary exchange rates, government fiscal policies, and changes in the prices of research studies, can have a significant effect on operations. While the Company maintains reserves for anticipated liabilities and carries various levels of insurance, the Company could be affected by civil, criminal, regulatory or administrative actions, claims, or proceedings.

Cash and Cash Equivalents

Cash and cash equivalents consist of all cash on hand, deposits, and funds invested in short-term investments with remaining maturities of three months or less at the time of purchase. The Company may maintain balances with its banks in excess of federally insured limits.

Short-Term Investments

Time deposits with remaining maturities of greater than three months but less than one year at the time of purchase are classified as short-term investments in the accompanying balance sheets.

Grant Income

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

Research and Development

Costs incurred in connection with research and development activities 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; (iv) facilities and other expenses, which include direct and allocated expenses for rent and maintenance of facilities and laboratory and other supplies; and (v) costs associated with preclinical activities and regulatory operations.

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 Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (ASC) Topic 740, Income Taxes, 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 financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the 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 some or all of 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 June 30, 2017, and December 31, 2016, the Company does not have any significant uncertain tax positions. If incurred, the Company would classify interest and penalties on uncertain tax positions as income tax expense.

Net Loss per Share

The Company’s basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. The diluted net 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. For purposes of this calculation, convertible preferred stock, convertible notes payable, stock options to purchase common stock, warrants, and unvested restricted stock awards are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented.

For all periods presented, all share and per share amounts have been retrospectively adjusted to reflect the exchange of each 2.3336572 shares of Aerpio capital stock and share based awards then outstanding, for 1 share of the Company’s common stock at the effective time of the Merger.

Stock-Based Compensation

The Company accounts for its stock-based compensation awards in accordance with FASB ASC Topic 718, Compensation – Stock Compensation. ASC 718 requires all stock-based payments to employees, including grants of employee stock options and restricted stock, to be recognized in the 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 subjective 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 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 Securities and Exchange Commission 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. Awards to non-employees are adjusted through share-based compensation expense as the award vests to reflect the current fair value of such awards and are expensed using an accelerated attribution model.

Fair Value of Financial Instruments

The Company’s financial instruments consist of cash equivalents, short-term investments, accounts receivable, and accounts payable. The Company values cash equivalents using quoted market prices. The valuation technique used to measure the fair value of short-term investments was based on net asset values corroborated with observable market data. The fair value of accounts receivable and accounts payable approximate the carrying value because of their 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. FASB ASC Topic 820, Fair Value Measurements and Disclosures, 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 six months ended June 30, 2017 or June 30, 2016. The assets of the Company measured on a recurring basis as of June 30, 2017 and December 31, 2016 basis are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
June 30, 2017
Assets:
Cash and cash equivalents	$	28,847,937	$	—	$	—	$	28,847,937
Short-term investments		—		50,000		—		50,000
Total assets	$	28,847,937	$	50,000	$	—	$	28,897,937
December 31, 2016
Assets:
Cash and cash equivalents	$	1,609,694	$	—	$	—	$	1,609,694
Short-term investments		—		50,000		—		50,000
Total assets	$	1,609,694	$	50,000	$	—	$	1,659,694

Concentrations of Credit Risk and Off-Balance Sheet Risk

Cash and cash equivalents and short-term investments are the only financial instruments that potentially subject the Company to concentrations of credit risk. At June 30, 2017 and December 31, 2016, all the Company’s cash was deposited in accounts at two principal financial institutions. The Company maintains its cash and cash equivalents and short-term investments with a high-quality, accredited financial institution 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 property, plant, 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).

Research and Development Costs

Research and development costs are expensed as incurred.

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 March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting.” This ASU is intended to simplify accounting for share-based payments and requires that excess tax benefits for share-based payments be recorded as a reduction of income tax expense and reflected within operating cash flows rather than being recorded within equity and reflected within financing cash flows. The ASU also provides an option for companies to recognize forfeitures as they occur rather than estimating the number of awards expected to be forfeited. The Company adopted this ASU on January 1, 2017 and is applying the new guidance related to excess tax benefits on a prospective basis. The Company has also elected to account for forfeitures of share-based payments as they occur. The effect of adoption was not material to the condensed consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases. This ASU will require lessees to recognize almost all leases on the balance sheet as a right-of-use asset and a lease liability. For income statement purposes, the FASB retained a dual model, requiring leases to be classified as finance leases or operating leases. This update is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently assessing the effect that adoption of the new standard will have on its condensed consolidated financial statements.

In August 2016, the FASB issued ASU No. 2016-15—Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force). The amendments in ASU 2016-15 address eight specific cash flow issues and apply to all entities that are required to present a statement of cash flows under FASB Accounting Standards Codification (FASB ASC) 230, Statement of Cash Flows. The amendments in ASU 2016-15 are effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption during an interim period. The Company has not yet adopted this update and is currently evaluating the impact of ASU No. 2016-15 on its condensed consolidated financial statements.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issue Task Force), or ASU 2016-18. This new standard addresses the diversity that exists in the classification and presentation of changes in restricted cash on the statement of cash flows. The amendments in ASU 2016-18 require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within the year of adoption, with early adoption permitted. We do not expect that the adoption of ASU 20116-18 will have a material impact on our condensed consolidated financial statements.

Related-Party Arrangements

6 Months Ended

Jun. 30, 2017

Related-Party Arrangements

3. Related-Party Arrangements

Aerpio was initially capitalized in December 2011 in a spinout transaction from Akebia Therapeutics, Inc. (Akebia) to enable more rapid development of its compounds. In connection with the spinout of Aerpio from Akebia, the companies entered into shared services agreements. Under the terms of the shared services agreements, Akebia and Aerpio obtained from and provided to each other certain services, as outlined below. These agreements were expired at December 31, 2016.

Below is a summary of the activities included in the statements of operations and comprehensive loss:

		Three Months Ended June 30,				Six Months Ended June 30,
Activity	Financial Statement Caption	2017		2016		2017		2016
Akebia related employee costs	Research and development operating expenses	$	—	$	—	$	—	$	12,923
Facility-related reimbursement	Other income, net		—		—		—		997

Accounts Payable and Accrued Expenses

6 Months Ended

Jun. 30, 2017

Payables And Accruals [Abstract]

Accounts Payable and Accrued Expenses

4. Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses are as follows:

	June 30,		December 31,
	2017		2016
Accounts payable	$	782,169	$	1,135,608
Professional fees		302,106		200,468
Accrued bonus		256,889		—
Accrued interest		—		483,442
Accrued vacation		106,686		52,835
Accrued project costs		354,995		541,158
Other		53,972		57,459
Total accounts payable and accrued expenses	$	1,856,817	$	2,470,970

Notes Payable to Investors	6 Months Ended
Notes Payable to Investors	Jun. 30, 2017
Debt Disclosure [Abstract]
Notes Payable to Investors	5. Notes Payable to Investors In March 2016, Aerpio entered into a senior secured convertible note financing (the “Convertible Notes” or the “Convertible Note Financing”) totaling approximately $9,000,000, with certain preferred investors of Aerpio. All preferred investors were invited to participate in the Convertible Notes Financing. At June 30, 2017 and December 31, 2016 the unamortized debt issuance costs related to Convertible Note financings was $0 and $75,561. In connection with the Convertible Note Financing, Aerpio’s Articles of Incorporation were amended such that any Aerpio preferred stockholder that did not participate in the Aerpio Convertible Note Financing would have their respective shares of Aerpio preferred stock automatically converted into Aerpio common stock using a 3-to-1 conversion ratio and such preferred stockholders would lose the right to representation on the Aerpio Board of Directors and other preferred rights. The Convertible Note Financing had two separate closings of approximately $4,500,000 each on April 14, 2016 and July 15, 2016. Certain Aerpio preferred stockholders chose not to participate in the Aerpio Convertible Note Financing and their respective Aerpio preferred stock was converted into shares of Aerpio common stock in April 2016 in accordance with the terms of the Articles of Incorporation. Aerpio treated this as an extinguishment of its preferred stock. The Convertible Notes accrued interest at 8% per annum, compounded annually. The Company incurred $138,312 of costs in association with the issuance of the Convertible Notes that were amortized over the expected life of the Convertible Notes, from the date of execution through October 31, 2016. The Convertible Notes were also subject to mandatory prepayment upon the occurrence of certain events, such as a liquidation, dissolution, or the sale of Aerpio. In addition, and prior to maturity, the Convertible Notes were automatically convertible into shares of Aerpio capital stock upon the occurrence of a sale of Aerpio’s capital stock in a single transaction resulting in gross proceeds to Aerpio of $30,000,000 (hereinafter referred to as an “Investor Sale”). The type and class of Aerpio capital stock of to be issued to the holder of each Convertible Note upon conversion would have been identical to the type and class of Aerpio capital stock issued in the Investor Sale. The holder of each Convertible Note was entitled to a number of shares of Aerpio capital determined by dividing (i) the outstanding principal amount of the Convertible Note plus any unpaid accrued interest by (ii) an amount equal to the price per share of Aerpio capital stock paid by the purchasers of such shares in connection with the Investor Sale. The Convertible Notes were secured by a first priority perfected security interest in all of the Aerpio’s assets. In October 2016 and February 2017, Aerpio executed an additional senior secured Convertible Note financings (the “Additional Convertible Notes” or the “Additional Convertible Note Financings”) totaling approximately $3,500,000 and $300,000 respectively, with certain preferred investors of Aerpio. The terms of the Additional Convertible Notes are identical to the Convertible Notes and are treated as extensions of the original Convertible Note Financing. The Company incurred $125,935 of costs associated with these transactions, which were amortized to the maturity date of March 31, 2017. In connection with the Additional Convertible Note Financings, the Convertible Notes were amended and their respective maturity dates were extended from October 31, 2016 to March 31, 2017. The amendments are accounted for as a modification for accounting purposes. In connection with the Merger (Note 1) the Convertible Notes and accrued interest were converted into the Company’s common stock.

Common Stock	6 Months Ended
Common Stock	Jun. 30, 2017
Equity [Abstract]
Common Stock	6. Common Stock As of June 30, 2017, and December 31, 2016, the Company had 300,000,000 and 17,440,436 shares, respectively, of authorized common stock with par value of $0.0001 per share. On March 15, 2017, in connection with the Merger, (Note 1) all the outstanding redeemable convertible preferred stock, was converted into 14,015,016 shares of the Company’s common stock and the Convertible Notes, both principal and accrued interest, were converted into 2,744,059 shares of the Company’s common stock. 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. Lock-up Agreements and Other Restrictions In connection with the Merger, each of the Company’s executive officers, directors, stockholders holding substantially all of the shares of common stock issued in exchange for shares held in Aerpio immediately prior to the Merger, certain other stockholders, and certain key employees, (the “Restricted Holders”), holding at the closing date of the Merger (the “Closing Date”) an aggregate of approximately 18.9 million shares of common stock, entered into lock-up agreements,(the “Lock-Up Agreements”), whereby they are restricted for a period of nine months after the Merger, or the Restricted Period, from certain sales or dispositions (including pledge) of all (or 80% in the case of the holders of 915,000 shares) of the Company’s common stock held by (or issuable to) them, (such restrictions together referred to as the “Lock-Up”). The foregoing restrictions will not apply to the resale of shares of common stock by any Restricted Holder in any registered secondary offering of equity securities by the Company (and, if such offering is underwritten, with the written consent of the lead or managing underwriter), or to certain other transfers customarily excepted. In addition, each Restricted Holder and any stockholders holding or beneficially owning 1% or more of our common stock after giving effect to the Merger, agreed, for a period of 12 months following the Closing Date, that it will not, directly or indirectly, effect or agree to effect any short sale (as defined in Rule 200 under Regulation SHO of the Exchange Act), whether or not against the box, establish any “put equivalent position” (as defined in Rule 16a-1(h) under the Exchange Act) with respect to the common stock, borrow or pre-borrow any shares of common stock, or grant any other right (including, without limitation, any put or call option) with respect to the common stock or with respect to any security that includes, relates to or derives any significant part of its value from the common stock or otherwise seek to hedge its position in the common stock. Anti-dilution protection Investors in the Offering have anti-dilution protection with respect to the shares of the Company’s common stock sold in the Offering such that if within six (6) months after the initial closing of the Offering the Company issues additional shares of common stock or common stock equivalents (subject to certain exceptions), for consideration per share less than the Offering Price, or the Lower Price, each such investor will be entitled to receive from the Company additional shares of common stock in an amount such that, when added to the number of shares of common stock initially purchased by such investor and still held of record and beneficially owned by such investor at the time of the dilutive issuance, or the Held Shares, will equal the number of shares of common stock that such investor’s Offering subscription amount for the Held Shares would have purchased at the Lower Price. Either (i) holders of a majority of the then-held Held Shares or (ii) a representative of the holders of the then-held Held Shares, which representative shall be appointed by three (3) investors who then hold the largest number of Held Shares, may waive the anti-dilution rights of all Offering investors with respect to a particular issuance by the Company. These anti-dilution rights were determined not to be a freestanding financial instrument and do not meet the definition of a derivative. Accordingly, the anti-dilution rights are embedded into the shares of the Company’s common stock and do not require separate accounting at June 30, 2017. Warrants to Purchase Common Stock At June 30, 2017, the Company had warrants outstanding for the purchase of 317,562 shares of the Company’s common stock at an exercise price of $5.00 per share. The warrants have a three-year term and expire on March 15, 2020. The Warrants were issued in connection with the Offering. At the expiration date of the warrant, 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 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 stock.

Preferred Stock

6 Months Ended

Jun. 30, 2017

Equity [Abstract]

Preferred Stock

7. Preferred Stock

At June 30, 2017, 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 June 30, 2017. In connection with the Merger (Note 1), all the Aerpio redeemable convertible preferred stock issued and outstanding prior to the Merger was converted into shares of the Company’s common stock.

At December 31, 2016, Aerpio’s redeemable convertible preferred stock consisted of the following:

•

Series A redeemable convertible preferred stock: 1,326,147 shares authorized and 1,239,338 shares issued and outstanding;

•

Series A1 redeemable convertible preferred stock: 8,368,247 shares authorized and 8,289,663 shares issued and outstanding; and

•

Series A2 redeemable convertible preferred stock: 4,660,573 shares authorized and 4,486,015 shares issued and outstanding.

All share and per share amounts are on an as converted basis to reflect the effect of the Merger. The rights, preferences, and privileges of the redeemable convertible preferred stock issued and outstanding prior to the Merger were as follows:

Voting

The holders of redeemable convertible preferred stock were entitled to the number of votes equal to the number of whole shares of Aerpio common stock into which the shares of redeemable convertible preferred stock were convertible. Except as provided by law or otherwise, the holders of redeemable convertible preferred stock voted together with the holders of Aerpio common stock as a single class. Certain significant actions required approval by at least 50% of the holders of redeemable convertible preferred stock voting as a single class on an as converted basis. Such significant actions include significant asset transfers, acquisitions, liquidation, amendments to the certificate of incorporation, new indebtedness, repurchase of common stock, changes in the authorized numbers of directors constituting the Board of Directors, and the declaration of dividends.

The holders of shares of redeemable convertible preferred stock were entitled to elect six members of Aerpio’s Board of Directors, which was subject to reduction to not less than four directors under certain circumstances. The holders of Aerpio common stock (including any holders of all shares of redeemable convertible preferred stock on an as converted basis) were entitled to elect two members of Aerpio’s Board of Directors, which was subject to reduction to one director under certain circumstances.

Dividends

Dividends were payable, if permitted by law, in accordance with redeemable convertible preferred stock terms or when and if declared by Aerpio Board of Directors. Prior to the issuance of Series A2 Preferred Stock, dividends on Series A Preferred Stock and Series A1 Preferred Stock were cumulative and accrued daily at a rate of 6% per annum whether or not declared. As part of the Series A2 Preferred Stock issuance, the dividend provisions for Series A Preferred Stock and Series A1 Preferred Stock were retrospectively amended to be noncumulative with the cumulative provision to begin after the Series A2 Preferred Stock issuance date at a rate of 6% per annum. This amendment did not significantly affect the nature of the Series A Preferred Stock and Series A1 Preferred Stock or their fair value. Accordingly, the amendment was treated as a modification for accounting purposes.

Liquidation

In the event of any voluntary or involuntary liquidation, dissolution, or winding-up of Aerpio, or upon the occurrence of a Deemed Liquidation Event, as defined, at the election of more than 50% of the holders of Series A2 Preferred Stock and Series A1 Preferred Stock, those holders were entitled to be paid, in preference to the holders of Series A Preferred Stock and Aerpio common stock, out of the assets of Aerpio available for distribution at $4.90 per share for Series A2 Preferred Stock and $3.97 per share for Series A1 Preferred Stock, plus any accrued but unpaid dividends. After the holders of Series A1 Preferred Stock and Series A2 Preferred Stock are satisfied, the holders of Series A Preferred Stock were paid at $4.27 per share, plus any accrued but unpaid dividends before any payment was made to the holders of Aerpio’s common stock.

In the event the assets of Aerpio available for distribution to stockholders were insufficient to pay the full amount to which the holder was entitled, the holders of Series A2 Preferred Stock and Series A1 Preferred Stock would share ratably any assets available for distribution in proportion to their relative original investment amounts. Any remaining assets of Aerpio would be distributed ratably among the holders of Series A Preferred Stock based upon aggregate applicable dividends accrued on Series A Preferred Stock not previously paid.

After the payment of all preferential amounts required to be paid to the holders of redeemable convertible preferred stock, the remaining assets available for distribution would be distributed among the holders of redeemable convertible preferred stock and Aerpio common stock based on the pro rata number of shares held by each holder, treating such securities as if they had been converted to Aerpio common stock immediately prior to such dissolution, liquidation, or winding-up of Aerpio.

Conversion

Each share of redeemable convertible preferred stock was convertible at the option of the holder, at any time and from time to time, into fully paid and non-assessable shares of Aerpio common stock. The initial conversion ratio was one share of redeemable convertible preferred stock for one share of Aerpio’s common stock. The applicable conversion rate was subject to adjustments upon the occurrence of certain events.

Each share of redeemable convertible preferred stock was automatically convertible into fully paid and non-assessable shares of Aerpio common stock at the then-applicable conversion ratio, as defined, upon either: (i) the closing of the sale of shares of Aerpio’s common stock to the public in an underwritten public offering at a price of $14.70 resulting in at least $40,000,000 of gross proceeds, or (ii) the date and time, or the occurrence of an event, specified by vote or written consent of the holders of more than 50% of the then outstanding shares of redeemable convertible preferred stock on an as-converted basis.

Aerpio evaluated each series of its redeemable convertible preferred stock and determined that each individual series is considered an equity host under ASC Topic 815, Derivatives and Hedging. In making this determination, Aerpio’s analysis followed the whole instrument approach, which compares an individual feature against the entire redeemable convertible preferred stock instrument that includes that feature. Aerpio’s analysis was based on a consideration of the economic characteristics and risks of each series of redeemable convertible preferred stock. More specifically, Aerpio evaluated all the stated and implied substantive terms and features, including: (i) whether the redeemable convertible preferred stock included redemption features, (ii) how and when any redemption features could be exercised, (iii) whether the holders of redeemable convertible preferred stock were entitled to dividends, (iv) the voting rights of the redeemable convertible preferred stock, and (v) the existence and nature of any conversion rights. Aerpio concluded that as the redeemable convertible preferred stock represents an equity host, the conversion feature included in all series of redeemable convertible preferred stock is clearly and closely related to the associated host instrument. Accordingly, the conversion feature of all series of redeemable convertible preferred stock was not considered an embedded derivative that required bifurcation.

Aerpio accounted for potentially beneficial conversion features under ASC Topic 470-20, Debt with Conversion and Other Options. At the time of each of the issuances of redeemable convertible preferred stock, Aerpio’s common stock into which each series of the redeemable convertible preferred stock was convertible had an estimated fair value less than the effective conversion prices of the redeemable convertible preferred stock. Therefore, there was no beneficial conversion element on the respective commitment dates.

In March 2016, in connection with the Convertible Note Financing described more fully in Note 5, Aerpio’s Articles of Incorporation were amended such that any preferred stockholder that did not participate in the Convertible Note Financing would have their respective shares of redeemable convertible preferred stock automatically converted into Aerpio common stock using a 3-to-1 conversion ratio and such preferred stockholders would lose the right to representation on Aerpio’s Board of Directors and other preferred rights. The amendment did not represent an increase in value to the preferred stockholders and was treated as a modification to the redeemable convertible preferred stock for accounting purposes. Certain shares of redeemable convertible preferred stock held by preferred stockholders that elected to not participate in the Convertible Note Financing were converted to shares in Aerpio’s common stock.

Redemption

The redeemable convertible preferred stock was redeemable on or after July 31, 2017, upon a request by more than 50% of the holders of redeemable convertible preferred stock then outstanding, payable in three annual installments commencing not more than 60 days following receipt by notice at a price equal to the greater of (i) the applicable original purchase price and dividends accrued but unpaid (Applicable Accrued Value), which is equal to its liquidation preference, or (ii) the redeemable convertible preferred stock fair value per share. Due to this redemption option, the redeemable convertible preferred stock was recorded in the mezzanine equity and subject to subsequent measurement under the guidance provided under ASC 480-10-S99. In accordance with that guidance, Aerpio elected to recognize changes in redemption value immediately as they occur through adjustments to the carrying amounts of the instruments at the end of each reporting period. As of December 31, 2016, the redemption values of all series of redeemable convertible preferred stock were equal to their respective Applicable Accrued Value. The fair values of redeemable convertible preferred stock were based upon a hybrid of the probability-weighted expected returns method and an option pricing model (OPM), which is a nonrecurring Level 3 fair value measurement within the fair value hierarchy. Under this hybrid model, share value is based on the probability weighted value of Aerpio in a potential public trading scenario, in which the redeemable convertible preferred stock converted to Aerpio common stock, and a second scenario in which equity value is allocated using the OPM. For the public trading scenario, Aerpio used the guideline public company method under the market approach.

Stock-Based Compensation

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

Pursuant to the Merger (Note 1), the Company assumed each option to purchase Aerpio common stock that remained outstanding under the Aerpio Therapeutics, Inc. 2011 Equity Incentive Plan (the “Plan”), whether vested or unvested, and converted it into an option to purchase such number of shares of the Company’s common stock equal to the number of shares of Aerpio common stock subject to the option immediately prior to the Merger, divided by the applicable Merger exchange rate of 2.3336572, with any fraction rounded down to the nearest whole number. The exercise price per share of each assumed option is equal to the exercise price of the Aerpio option prior to the assumption, multiplied by the applicable Merger exchange rate of 2.3336572, rounded up to the nearest whole cent. The terms of the 2011 Plan continue to govern the options covering an aggregate of 898,692 shares of the Company’s common stock at June 30, 2017 and December 31, 2016, subject to awards assumed by the Company, except that all references in the 2011 Plan to Aerpio, will now be the Company. In addition, each unvested share of Aerpio restricted common stock issued under the 2011 Plan that was outstanding immediately prior to the effective time of the Merger, was converted by virtue of the Merger into restricted common stock of the Company, equal to the number of shares of Aerpio common stock subject to the unvested shares of Aerpio restricted common stock immediately prior to the Merger divided by the applicable Merger exchange rate of 2.3336572, with any fraction rounded down to the nearest whole number.

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 2011 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. No awards were granted under the 2017 Plan as of June 30, 2017.

Stock Options

The options granted generally vest over 48 months. For employees with less than one year’s service, options vest in installments of 25% at the one-year anniversary and thereafter in 36 equal monthly installments beginning in the 13th month after the initial Vesting Commencement Date (as defined), subject to the employee’s continuous service with the Company. Options granted to other employees vest in 48 equal monthly installments after the initial Vesting Commencement Date, 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. No option awards were granted in the six months ended June 30, 2017 and one option award was granted for 50,228 shares in the six months ended June 30, 2016.

The following table summarizes the stock option activity during the six-months ended June 30, 2017:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding, January 1, 2017		927,592		$	1.70		7.48	$	1,030,217
Granted		—			—
Exercised		(25,729	)		1.40
Expired/cancelled		(2,901	)		2.11
Outstanding, June 30, 2017		898,962		$	1.70	6.87		$	2,963,449
Expected to vest, June 30, 2017		231,733		$	1.80	7.91			742,130
Options exercisable, June 30, 2017		667,229		$	1.67		6.50	$	2,221,319

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.

Compensation expense for stock options was $38,954 and $42,225 for the three months ended June 30, 2017 and 2016, respectively and $120,075 and $85,041 for the six months ended June 30, 2017 and 2016 respectively. As of June 30, 2017, there was $226,405 of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted average period of 2.0 years.

Restricted Stock

Shares of restricted stock generally have similar vesting terms as stock options. A summary of the Company’s restricted stock activity and related information during the six months ended June 30, 2017 is as follows:

	Shares			Weighted Average Grant Date Fair Value
Nonvested, January 1, 2017		241,096		$	1.91
Granted		—			—
Vested		(67,126	)	$	1.77
Forfeited		(5,246	)	$	2.20
Nonvested, June 30, 2017		168,724		$	1.94

The Company recognized compensation expense for restricted stock of $72,570 and $77,325 for the three months ended June 30, 2017 and 2016, respectively, and $146,834 and 159,724 for the six months ended June 30, 2017 and 2016 respectively. As of June 30, 2017, there was $288,016 of unrecognized compensation cost related to these restricted stock grants, which is expected to be recognized over a weighted average period of 1.2 years.

Compensation Expense Summary

The Company has recognized the following compensation cost related to employee and non-employee stock-based compensation activity:

	Three Months Ended June 30				Six Months Ended June 30
	2017		2016		2017		2016
Research and development	$	73,033	$	74,944	$	188,335	$	156,677
General and administrative		38,491		44,606		78,574		88,088
Total	$	111,524	$	119,550	$	266,909	$	244,765

The Company uses the Black-Scholes option pricing model to determine the estimated fair value for stock-based awards. Option pricing models require the input of various subjective assumptions, including the option’s expected life, expected dividend yield, price volatility and risk free interest rate of the underlying stock. Accordingly, the weighted-average fair value of the options granted during the three and six months ended June 30, 2016 was $1.22. The calculation was based on the following assumptions.

	Three Months Ended		Six Months Ended
	June 30, 2016		June 30, 2016
Expected term (years)		6.00		6.00
Risk-free interest rate		1.39%		1.39%
Expected volatility		78.00%		78.00%
Expected dividend yield		0.00%		0.00%

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The Company did not record a current or deferred income tax expense of benefit for the six months ended June 30, 2017 and 2016, due to the Company’s net losses and increases in its deferred tax asset valuation allowance.

Net Loss Per Share

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

Net Loss per Share

10. Net Loss per Share

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

	Three Months Ended June 30						Six Months Ended June 30
	2017			2016			2017			2016
Net loss and comprehensive loss	$	(5,520,307	)	$	(4,385,262	)	$	(10,516,010	)	$	(8,579,961	)
Extinguishment of preferred stock		—			224,224			—			224,224
Accretion of preferred stock to redemption value		—			(1,028,121	)		(943,297	)		(2,043,492	)
Net loss attributable to common stockholders	$	(5,520,307	)	$	(5,189,159	)	$	(11,459,307	)	$	(10,399,229	)
Net loss per share attributable to common stockholders, basic and diluted	$	(0.21	)	$	(6.30	)	$	(0.70	)	$	(13.33	)
Weighted average common shares used in computing net loss per share attributable to common stockholders, basic and diluted		26,895,164			823,097			16,313,324			780,152

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

	June 30
	2017		2016
Convertible preferred stock (if converted)		—		14,141,112
Notes and accrued interest (if converted)		—		944,048
Options to purchase common stock		898,962		927,592
Unvested restricted stock		168,724		344,574
Warrants to purchase common stock		317,562		—

Commitments and Contingencies

6 Months Ended

Jun. 30, 2017

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

11. Commitments and Contingencies

The Company contracts with various organizations to conduct research and development activities. In addition, the Company is a party to a lease covering 7,580 square feet of space in Cincinnati, Ohio that expires in June 2018. Total rent expense for all operating leases was $51,153 and $59,924 for the three months ended June 30, 2017 and 2016, and $102,442 and $108,104 the six months ended June 30, 2017 and 2016 respectively. The lease agreement contains free rent, escalating rent payments and reimbursement for tenant improvements that amounted to $0 and $46,390 in the three and six months ended June 30, 2016, respectively. Rent expense is recorded on the straight-line basis over the initial term with the differences between rent expense and rent payments recorded as deferred rent. As of June 30, 2017, the Company had deferred rent of $46,372, which is included in accrued expenses in the accompanying condensed consolidated balance sheet. As of June 30, 2017, non-cancelable future minimum lease payments under the existing operating lease were $105,735. As of June 30, 2017, future payments related to operating leases activities are presented in the table below.

2017

2018

2019 and

Thereafter

Total

Operating leases

52,757

52,978

—

105,735

The Company contracts with various organizations to conduct research and development activities, including clinical trial organizations to manage clinical trial activities. The scope of the services under these research and development contracts can be modified and the contracts cancelled by the Company upon written notice. In the event of a cancellation, the Company would only be liable for the cost and expenses incurred to date.

Employee Stock Purchase Plan	6 Months Ended
Employee Stock Purchase Plan	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Employee Stock Purchase Plan	12. Employee Stock Purchase Plan In March 2017, the Board of Directors adopted and the stockholders approved, the Employee Stock Purchase Plan (the “ESPP”), that became effective in April 2017. The ESPP provides for the issuance of up to 300,000 shares of the Company’s common stock for the purchases made under the ESPP. The ESPP 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 one percent (1%) of the shares of the Company’s common stock outstanding on the last day of the immediately preceding year or such smaller increase as determined by the Company’s Board of Directors. The Board of Directors has not yet determined the timing for the offering periods under the ESPP.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2017

Accounting Policies [Abstract]

Basis of Presentation

Segment Information

Use of Estimates

Cash and Cash Equivalents

Short-Term Investments

Time deposits with remaining maturities of greater than three months but less than one year at the time of purchase are classified as short-term investments in the accompanying balance sheets.

Grant Income

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

Research and Development Costs

Research and Development

The Company enters into consulting, research, and other agreements with commercial firms, researchers, universities, and others for the provision of goods and services.

Research and Development Costs

Research and development costs are expensed as incurred.

Patents

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

Income Taxes

Net Loss Per Share

Net Loss per Share

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
June 30, 2017
Assets:
Cash and cash equivalents	$	28,847,937	$	—	$	—	$	28,847,937
Short-term investments		—		50,000		—		50,000
Total assets	$	28,847,937	$	50,000	$	—	$	28,897,937
December 31, 2016
Assets:
Cash and cash equivalents	$	1,609,694	$	—	$	—	$	1,609,694
Short-term investments		—		50,000		—		50,000
Total assets	$	1,609,694	$	50,000	$	—	$	1,659,694

Concentrations of Credit Risk and Off-Balance Sheet Risk

Comprehensive Loss

Furniture and Equipment

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2017

Accounting Policies [Abstract]

Schedule of Assets Measured on Recurring Basis

The assets of the Company measured on a recurring basis as of June 30, 2017 and December 31, 2016 basis are summarized below:

	Fair Value Measurements Using
	Level 1		Level 2		Level 3		Total
June 30, 2017
Assets:
Cash and cash equivalents	$	28,847,937	$	—	$	—	$	28,847,937
Short-term investments		—		50,000		—		50,000
Total assets	$	28,847,937	$	50,000	$	—	$	28,897,937
December 31, 2016
Assets:
Cash and cash equivalents	$	1,609,694	$	—	$	—	$	1,609,694
Short-term investments		—		50,000		—		50,000
Total assets	$	1,609,694	$	50,000	$	—	$	1,659,694

Related-Party Arrangements (Tables)

6 Months Ended

Jun. 30, 2017

Akebia [Member]

Summary of activities included in statements of operations and comprehensive loss

Below is a summary of the activities included in the statements of operations and comprehensive loss:

		Three Months Ended June 30,				Six Months Ended June 30,
Activity	Financial Statement Caption	2017		2016		2017		2016
Akebia related employee costs	Research and development operating expenses	$	—	$	—	$	—	$	12,923
Facility-related reimbursement	Other income, net		—		—		—		997

Accounts Payable and Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2017

Payables And Accruals [Abstract]

Schedule of Accounts Payable and Accrued Expenses

	June 30,		December 31,
	2017		2016
Accounts payable	$	782,169	$	1,135,608
Professional fees		302,106		200,468
Accrued bonus		256,889		—
Accrued interest		—		483,442
Accrued vacation		106,686		52,835
Accrued project costs		354,995		541,158
Other		53,972		57,459
Total accounts payable and accrued expenses	$	1,856,817	$	2,470,970

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of stock option activity

The following table summarizes the stock option activity during the six-months ended June 30, 2017:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding, January 1, 2017		927,592		$	1.70		7.48	$	1,030,217
Granted		—			—
Exercised		(25,729	)		1.40
Expired/cancelled		(2,901	)		2.11
Outstanding, June 30, 2017		898,962		$	1.70	6.87		$	2,963,449
Expected to vest, June 30, 2017		231,733		$	1.80	7.91			742,130
Options exercisable, June 30, 2017		667,229		$	1.67		6.50	$	2,221,319

Summary of restricted stock activity

A summary of the Company’s restricted stock activity and related information during the six months ended June 30, 2017 is as follows:

	Shares			Weighted Average Grant Date Fair Value
Nonvested, January 1, 2017		241,096		$	1.91
Granted		—			—
Vested		(67,126	)	$	1.77
Forfeited		(5,246	)	$	2.20
Nonvested, June 30, 2017		168,724		$	1.94

Summary of recognized compensation cost related to employee and non-employee stock-based compensation activity

The Company has recognized the following compensation cost related to employee and non-employee stock-based compensation activity:

	Three Months Ended June 30				Six Months Ended June 30
	2017		2016		2017		2016
Research and development	$	73,033	$	74,944	$	188,335	$	156,677
General and administrative		38,491		44,606		78,574		88,088
Total	$	111,524	$	119,550	$	266,909	$	244,765

Stock options valuation assumptions

The calculation was based on the following assumptions.

	Three Months Ended		Six Months Ended
	June 30, 2016		June 30, 2016
Expected term (years)		6.00		6.00
Risk-free interest rate		1.39%		1.39%
Expected volatility		78.00%		78.00%
Expected dividend yield		0.00%		0.00%

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

Schedule of computation of basic and diluted net loss per share

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

	Three Months Ended June 30						Six Months Ended June 30
	2017			2016			2017			2016
Net loss and comprehensive loss	$	(5,520,307	)	$	(4,385,262	)	$	(10,516,010	)	$	(8,579,961	)
Extinguishment of preferred stock		—			224,224			—			224,224
Accretion of preferred stock to redemption value		—			(1,028,121	)		(943,297	)		(2,043,492	)
Net loss attributable to common stockholders	$	(5,520,307	)	$	(5,189,159	)	$	(11,459,307	)	$	(10,399,229	)
Net loss per share attributable to common stockholders, basic and diluted	$	(0.21	)	$	(6.30	)	$	(0.70	)	$	(13.33	)
Weighted average common shares used in computing net loss per share attributable to common stockholders, basic and diluted		26,895,164			823,097			16,313,324			780,152

Schedule of weighted average common stock equivalents excluded from calculation of diluted net loss per share

	June 30
	2017		2016
Convertible preferred stock (if converted)		—		14,141,112
Notes and accrued interest (if converted)		—		944,048
Options to purchase common stock		898,962		927,592
Unvested restricted stock		168,724		344,574
Warrants to purchase common stock		317,562		—

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2017

Commitments And Contingencies Disclosure [Abstract]

Schedule of future payments related to operating leases

As of June 30, 2017, future payments related to operating leases activities are presented in the table below

2017

2018

2019 and

Thereafter

Total

Operating leases

52,757

52,978

—

105,735

Nature of Organization and Operations - Additional Information (Detail)		6 Months Ended
	Mar. 15, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Mar. 14, 2017 shares	Mar. 10, 2017 $ / shares shares	Mar. 03, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares
Class Of Stock [Line Items]
Common stock, shares authorized		300,000,000		300,000,000	100,000,000	17,440,436
Common stock, par value \| $ / shares		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized		10,000,000		10,000,000	10,000,000
Preferred stock, par value \| $ / shares		$ 0.0001		$ 0.0001	$ 0.0001
Capital stock conversion basis ratio	2.3336572
Common stock, shares outstanding		27,070,038				1,240,925
Net proceeds of common stock issued to private placement \| $		$ 37,163,390
Warrants issued to purchase common stock, exercise price \| $ / shares		$ 5.00
Minimum [Member]
Class Of Stock [Line Items]
Percentage of Interest owned in the combined enterprise	50.00%
Common Stock
Class Of Stock [Line Items]
Common stock issued to private placement		8,049,555
Net proceeds of common stock issued to private placement \| $		$ 805
Zeta Acquisition Corp. II [Member]
Class Of Stock [Line Items]
Number of shares surrendered for cancellation	4,000,000
Common stock, shares outstanding			5,000,000
Issuance of warrants term	3 years
Number of warrants issued to purchase common stock	317,562
Warrants issued to purchase common stock, exercise price \| $ / shares	$ 5.00
Zeta Acquisition Corp. II [Member] \| Common Stock
Class Of Stock [Line Items]
Common stock issued to private placement	8,049,555
Common stock issued to private placement, price per share \| $ / shares	$ 5.00
Net proceeds of common stock issued to private placement \| $	$ 37,200,000

Summary of Significant Accounting Policies - Additional Information (Detail)		6 Months Ended
	Mar. 15, 2017	Jun. 30, 2017 USD ($) Segment Institution	Dec. 31, 2016 USD ($) Institution
Summary Of Significant Accounting Policies [Line Items]
Number of operating segment \| Segment		1
Significant uncertain tax positions \| $		$ 0	$ 0
Capital stock conversion basis ratio	2.3336572
Number of principal financial institutions in cash deposit \| Institution		2	2
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

Summary of Significant Accounting Policies (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Assets:
Cash and cash equivalents	$ 28,847,937	$ 1,609,694
Short-term investments	50,000	50,000
Total assets	28,897,937	1,659,694
Level 1 [Member]
Assets:
Cash and cash equivalents	28,847,937	1,609,694
Total assets	28,847,937	1,609,694
Level 2 [Member]
Assets:
Short-term investments	50,000	50,000
Total assets	$ 50,000	$ 50,000

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References + Details

Related-Party Arrangements (Detail) - USD ($)	3 Months Ended		6 Months Ended
Related-Party Arrangements (Detail) - USD ($)	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Related Party Transaction [Line Items]
Research and development	$ 3,169,115	$ 2,903,564	$ 5,424,699	$ 5,893,122
Other income, net				997
Akebia [Member] \| Employee Costs [Member]
Related Party Transaction [Line Items]
Research and development				12,923
Akebia [Member] \| Facility Related Reimbursement [Member]
Related Party Transaction [Line Items]
Other income, net				$ 997

Accounts Payable and Accrued Expenses (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accounts payable	$ 782,169	$ 1,135,608
Professional fees	302,106	200,468
Accrued bonus	256,889
Accrued interest		483,442
Accrued vacation	106,686	52,835
Accrued project costs	354,995	541,158
Other	53,972	57,459
Total accounts payable and accrued expenses	$ 1,856,817	$ 2,470,970

Notes Payable to Investors - Additional Information (Detail)	1 Months Ended			6 Months Ended
	Feb. 28, 2017 USD ($)	Oct. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jul. 15, 2016 USD ($)	Apr. 14, 2016 USD ($)
Convertible Note Financing [Member]
Debt Instrument [Line Items]
Convertible notes payable			$ 9,000,000			$ 4,500,000	$ 4,500,000
Conversion description				In connection with the Convertible Note Financing, Aerpio’s Articles of Incorporation were amended such that any Aerpio preferred stockholder that did not participate in the Aerpio Convertible Note Financing would have their respective shares of Aerpio preferred stock automatically converted into Aerpio common stock using a 3-to-1 conversion ratio and such preferred stockholders would lose the right to representation on the Aerpio Board of Directors and other preferred rights.
Unamortized debt issuance costs				$ 0	$ 75,561
Conversion ratio			0.33
Debt instrument, accrued interest rate				8.00%
Debt issuance cost				$ 138,312
Gross proceeds from sale of capital stock				$ 30,000,000
Additional Convertible Note Financings [Member]
Debt Instrument [Line Items]
Convertible notes payable	$ 300,000	$ 3,500,000
Debt issuance cost	$ 125,935	$ 125,935
Maturity date	Mar. 31, 2017	Mar. 31, 2017

Common Stock - Additional Information (Detail) - USD ($)			6 Months Ended
	Jun. 30, 2017	Mar. 15, 2017	Jun. 30, 2017	Mar. 10, 2017	Mar. 03, 2017	Dec. 31, 2016
Class Of Stock [Line Items]
Common stock, shares authorized	300,000,000		300,000,000	300,000,000	100,000,000	17,440,436
Common stock, par value	$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Dividends common stock declared or paid			$ 0
Number of shares of common stock in lock-up agreements	18,900,000		18,900,000
Restricted period for shares of common stock in lock-up agreements			9 months
Restricted percentage of common stock for holders of 915,000 shares			80.00%
Number of shares of common stockholders with 80% restriction	915,000		915,000
Period agreed by common stockholder not to effect short sale after merger			12 months
Warrants outstanding	317,562		317,562
Warrants exercise price per share	$ 5.00		$ 5.00
Warrants term	3 years
Warrants expiration date			Mar. 15, 2020
Minimum [Member]
Class Of Stock [Line Items]
Percentage of common stockholder agreed not to effect short sale after merger			1.00%
Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of preferred stock, Shares		14,015,016
Convertible Notes [Member]
Class Of Stock [Line Items]
Conversion of convertible notes and accrued interest, Shares		2,744,059

Preferred Stock - Additional Information (Detail)	1 Months Ended	6 Months Ended
Preferred Stock - Additional Information (Detail)	Mar. 31, 2016	Jun. 30, 2017 USD ($) Director Installment $ / shares shares	Mar. 10, 2017 $ / shares shares	Mar. 03, 2017 $ / shares shares	Dec. 31, 2016 shares
Temporary Equity [Line Items]
Preferred stock, shares authorized		10,000,000	10,000,000	10,000,000
Preferred stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares issued		0
Preferred stock, shares outstanding		0
Redeemable convertible preferred stock, voting rights		The holders of redeemable convertible preferred stock were entitled to the number of votes equal to the number of whole shares of Aerpio common stock into which the shares of redeemable convertible preferred stock were convertible. Except as provided by law or otherwise, the holders of redeemable convertible preferred stock voted together with the holders of Aerpio common stock as a single class. Certain significant actions required approval by at least 50% of the holders of redeemable convertible preferred stock voting as a single class on an as converted basis.
Redeemable convertible preferred stock conversion percentage	300.00%	100.00%
Redeemable convertible preferred stock redemption date		Jul. 31, 2017
Minimum [Member]
Temporary Equity [Line Items]
Percentage of redeemable convertible preferred stock voting rights		50.00%
Proceeds from Issuance Initial Public Offering \| $		$ 40,000,000
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized					1,326,147
Redeemable convertible preferred stock, shares issued					1,239,338
Redeemable convertible preferred, shares outstanding					1,239,338
Redeemable convertible preferred stock distribution to be paid \| $ / shares		$ 4.27
Series A1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized					8,368,247
Redeemable convertible preferred stock, shares issued					8,289,663
Redeemable convertible preferred, shares outstanding					8,289,663
Redeemable convertible preferred stock distribution to be paid \| $ / shares		$ 3.97
Series A2 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares authorized					4,660,573
Redeemable convertible preferred stock, shares issued					4,486,015
Redeemable convertible preferred, shares outstanding					4,486,015
Redeemable convertible preferred stock, dividend rate, percentage		6.00%
Redeemable convertible preferred stock distribution to be paid \| $ / shares		$ 4.90
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Redeemable convertible preferred, shares outstanding					14,015,016
Number of board of directors appointed by redeemable convertible preferred shares holders \| Director		6
Number of board of directors appointed by common shares holders \| Director		2
Number of board of directors appointed by common shares holders under certain circumstances \| Director		1
Share Price \| $ / shares		$ 14.70
Number of installments payable \| Installment		3
Annual installment payable commencing period		60 days
Redeemable Convertible Preferred Stock \| Minimum [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock conversion basis percentage		50.00%
Redeemable Convertible Preferred Stock \| Maximum [Member]
Temporary Equity [Line Items]
Number of board of directors appointed by redeemable convertible preferred shares holders under certain circumstances \| Director		4
Series A Redeemable Convertible Preferred Stock and Series A1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, dividend rate, percentage		6.00%

Stock-Based Compensation - Additional Information (Detail)		3 Months Ended		6 Months Ended
	Mar. 15, 2017	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2016 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Merger exchange rate	2.3336572
Aggregate number of common stock		898,962		898,962		927,592
Unrecognized compensation cost related to stock options \| $		$ 226,405		$ 226,405
Weighted-average fair value of options granted \| $ / shares			$ 1.22		$ 1.22
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of awards granted				0	50,228
Vesting period				48 months
Term of options to be granted				10 years
Compensation expense for stock options \| $		$ 38,954	$ 42,225	$ 120,075	$ 85,041
Weighted average period expected to be recognized		2 years
Stock Option [Member] \| One-year Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage				25.00%
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense for stock options \| $		$ 72,570	$ 77,325	$ 146,834	$ 159,724
Weighted average period expected to be recognized				1 year 2 months 12 days
Unrecognized compensation cost related to restricted stock grants \| $		$ 288,016		$ 288,016
2011 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Merger exchange rate	2.3336572
Aggregate number of common stock		898,692		898,692		898,692
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		4,600,000
Percentage applied to the outstanding shares as annual increase in number of shares authorized for issuance				4.00%
Number of awards granted				0

Stock-Based Compensation - 2 (Detail) - USD ($)	6 Months Ended	12 Months Ended
Stock-Based Compensation - 2 (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding at beginning balance	927,592
Shares, Exercised	(25,729)
Shares, Expired/cancelled	(2,901)
Shares, Outstanding at ending balance	898,962	927,592
Shares, Expected to vest	231,733
Shares, Options exercisable	667,229
Weighted Average Exercise Price, Outstanding at beginning balance	$ 1.70
Weighted Average Exercise Price, Exercised	1.40
Weighted Average Exercise Price, Expired/cancelled	2.11
Weighted Average Exercise Price, Outstanding at ending balance	1.70	$ 1.70
Weighted Average Exercise Price, Expected to vest	1.80
Weighted Average Exercise Price, Options exercisable	$ 1.67
Weighted Average Remaining Contractual Term, Outstanding	6 years 10 months 14 days	7 years 5 months 23 days
Weighted Average Remaining Contractual Term, Expected to vest	7 years 10 months 28 days
Weighted Average Remaining Contractual Term, Options exercisable	6 years 6 months
Aggregate Intrinsic Value, Outstanding	$ 2,963,449	$ 1,030,217
Aggregate Intrinsic Value, Expected to vest	742,130
Aggregate Intrinsic Value, Options exercisable	$ 2,221,319

Stock-Based Compensation - 3 (Detail) - Restricted Stock [Member]	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Nonvested beginning balance \| shares	241,096
Shares, Vested \| shares	(67,126)
Shares, Forfeited \| shares	(5,246)
Shares, Nonvested ending balance \| shares	168,724
Weighted Average Grant Date Fair Value, Nonvested beginning balance \| $ / shares	$ 1.91
Weighted Average Grant Date Fair Value, Vested \| $ / shares	1.77
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	2.20
Weighted Average Grant Date Fair Value, Nonvested ending balance \| $ / shares	$ 1.94

Stock-Based Compensation - 4 (Detail) - USD ($)	3 Months Ended		6 Months Ended
Stock-Based Compensation - 4 (Detail) - USD ($)	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 111,524	$ 119,550	$ 266,909	$ 244,765
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	73,033	74,944	188,335	156,677
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 38,491	$ 44,606	$ 78,574	$ 88,088

Stock-Based Compensation - Stock Options Valuation Assumptions (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (years)	6 years	6 years
Risk-free interest rate	1.39%	1.39%
Expected volatility	78.00%	78.00%
Expected dividend yield	0.00%	0.00%

Income Taxes - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Current income tax expense or benefit	$ 0	$ 0
Deferred income tax expense or benefit	$ 0	$ 0

Net Loss Per Share (Detail) - USD ($)	3 Months Ended		6 Months Ended
Net Loss Per Share (Detail) - USD ($)	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net loss and comprehensive loss	$ (5,520,307)	$ (4,385,262)	$ (10,516,010)	$ (8,579,961)
Extinguishment of preferred stock		224,224		224,224
Accretion of preferred stock to redemption value		(1,028,121)	(943,297)	(2,043,492)
Net Loss attributable to common stockholders	$ (5,520,307)	$ (5,189,159)	$ (11,459,307)	$ (10,399,229)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.21)	$ (6.30)	$ (0.70)	$ (13.33)
Weighted average number of common shares used in computing net loss per share attributable to common stockholders, basic and diluted	26,895,164	823,097	16,313,324	780,152

Schedule of Weighted Average Common Stock Equivalents were Excluded from Calculation of Diluted Net Loss per Share (Detail) - Weighted Average [Member] - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock Option [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	898,962	927,592
Unvested Restricted 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	168,724	344,574
Warrants 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	317,562
Convertible Preferred Stock (If Converted) [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		14,141,112
Notes and Accrued Interest (If Converted) [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		944,048

Commitments and Contingencies - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) ft²	Jun. 30, 2016 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Area of lease property \| ft²			7,580
Lease expiration date			Jun. 30, 2018
Total operating leases rent expense	$ 51,153	$ 59,924	$ 102,442	$ 108,104
Lease agreement allowances for tenant improvements		$ 0		$ 46,390
Deferred rent included in accrued expenses	46,372		46,372
Non-cancellable future minimum operating lease payments	$ 105,735		$ 105,735

Commitments and Contingencies (Detail)	Jun. 30, 2017 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating leases, 2017	$ 52,757
Operating leases, 2018	52,978
Operating leases, Total	$ 105,735

Employee Stock Purchase Plan - Additional Information (Detail) - Common Stock - Employee Stock Purchase Plan [Member]	1 Months Ended
	Mar. 31, 2017 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares provided for issuance	300,000
Percentage of annual increase in number of shares reserved for issuance	1.00%