Apellis Pharmaceuticals (APLS) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 24, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	APLS
Entity Registrant Name	Apellis Pharmaceuticals, Inc.
Entity Central Index Key	1,492,422
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		55,941,896

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 152,930,977	$ 175,643,529
Refundable research and development credit	1,828,565	1,297,361
Prepaid assets	8,121,602	5,059,593
Other current assets	205,713	14,823
Total current assets	163,086,857	182,015,306
Other assets	116,150	116,150
Total assets	163,203,007	182,131,456
Current liabilities:
Accounts payable	4,585,058	3,663,253
Accrued expenses	2,709,801	2,890,705
Total current liabilities	7,294,859	6,553,958
Long-term liabilities:
Term loan facility	20,015,568	19,806,944
Promissory note - related party	6,600,475	6,583,402
Common stock warrant liability	250,000	244,292
Total liabilities	34,160,902	33,188,596
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized, and zero shares issued and outstanding at December 31, 2017 and March 31, 2018	0	0
Common stock, $0.0001 par value; 200,000,000 shares authorized at December 31, 2017 and March 31, 2018 and 50,334,152 shares issued and outstanding at December 31, 2017 and 50,429,020 shares issued and outstanding at March 31, 2018	5,042	5,033
Additional paid in capital	300,037,020	298,201,480
Accumulated deficit	(170,999,957)	(149,263,653)
Total stockholders' equity	129,042,105	148,942,860
Total liabilities and stockholders' equity	$ 163,203,007	$ 182,131,456

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, issued	50,429,020	50,334,152
Common stock, outstanding	50,429,020	50,334,152

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses:
Research and development	$ 17,402,890	$ 7,231,084
General and administrative	4,035,255	1,821,409
Operating loss	(21,438,145)	(9,052,493)
Interest income (expense), net	(266,686)	10,112
Other expense, net	(31,473)	(8,392)
Net loss and comprehensive loss	$ (21,736,304)	$ (9,050,773)
Net loss per common share, basic and diluted	$ (0.43)	$ (1.07)
Weighted-average number of common shares used in net loss per common share, basic and diluted	50,353,812	8,428,366

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Changes in Stockholder's Equity - 3 months ended Mar. 31, 2018 - USD ($)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2017	$ 148,942,860	$ 5,033	$ 298,201,480	$ (149,263,653)
Beginning balance, Shares at Dec. 31, 2017		50,334,152
Issuance of common stock upon exercise of stock options	225,361	$ 9	225,352
Issuance of common stock upon exercise of stock options, Shares		94,868
Share-based compensation expense	1,610,188		1,610,188
Net loss	(21,736,304)			(21,736,304)
Ending balance at Mar. 31, 2018	$ 129,042,105	$ 5,042	$ 300,037,020	$ (170,999,957)
Ending balance, Shares at Mar. 31, 2018		50,429,020

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net loss	$ (21,736,304)	$ (9,050,773)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	1,610,188	327,909
Loss from remeasurement of fair value of warrants	5,708
Accretion of discounts	17,073
Amortization	208,624
Changes in operating assets and liabilities:
Refundable research and development credit	(531,204)	(122,397)
Prepaid assets	(3,062,009)
Other current assets	(188,226)	217,759
Other assets		26,111
Accounts payable	921,805	(180,331)
Accrued expenses	(180,904)	354,772
Net cash used in operating activities	(22,935,249)	(8,426,950)
Financing Activities
Deferred issuance costs	(2,664)
Proceeds from exercise of stock options	225,361
Net cash provided by financing activities	222,697
Net decrease in cash and cash equivalents	(22,712,552)	(8,426,950)
Cash and cash equivalents at beginning of period	175,643,529	24,863,488
Cash and cash equivalents at end of period	$ 152,930,977	$ 16,436,538

Nature of Organization and Oper

Nature of Organization and Operations	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Organization and Operations	1. Nature of Organization and Operations Apellis Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on the development of novel therapeutic compounds to treat disease through the inhibition of the complement system, which is an integral component of the immune system, at the level of C3, the central protein in the complement cascade. The Company was incorporated in September 2009 under the laws of the State of Delaware and has its principal office in Crestwood, Kentucky. The Company’s operations since inception have been limited to organizing and staffing the Company, acquiring rights to product candidates, business planning, raising capital and developing its product candidates. The Company is subject to risks common in the biotechnology industry including, but not limited to, raising additional capital, development by its competitors of new technological innovations, its ability to successfully complete preclinical and clinical development of product candidates and receive timely regulatory approval of products, market acceptance of the Company’s products, protection of proprietary technology, healthcare cost containment initiatives, and compliance with governmental regulations, including those of the U.S. Food and Drug Administration (“FDA”). Liquidity and Financial Condition The accompanying unaudited condensed consolidated financial statements have been prepared on the basis of the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. As of April 30, 2018, the date of issuance of these unaudited condensed consolidated financial statements, the Company believes that its cash and cash equivalents as of March 31, 2018 of $152.9 million, together with the net proceeds from its follow-on offering (“2018 follow-on offering”) of $131.3 million, will be sufficient to fund its operations into the third quarter of 2019. The future viability beyond that point is dependent on its ability to raise additional capital to finance its operations. The Company is subject to risks common to other life science companies in the development stage including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing, and compliance with FDA and other government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability. Management’s plans in order to meet its short-term and longer term operating cash flow requirements include obtaining additional funding. There are uncertainties associated with the Company’s ability to (1) obtain additional debt or equity financing (2) enter into collaborative agreements with strategic partners, and (3) succeed in its future operations. If the Company is not able to obtain the required capital to fund its operations from any of these, or is not able to obtain such funding on terms that are favorable to the Company, it could be forced to delay, reduce or eliminate its research and development programs or future commercialization efforts and its business could be materially harmed.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	2. Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Apellis Australia Pty Ltd. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and, accordingly, the balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of the Company’s financial information. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 19, 2018. Reverse Stock Split On October 27, 2017, the Company effectuated a l-for-2.133 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on October 27, 2017. The reverse stock split resulted in an adjustment to the conversion prices of its convertible preferred stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying unaudited condensed consolidated financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders’ deficit reflects the reverse stock split by reclassifying from “common stock” to “additional paid-in capital” in an amount equal to the par value of the decreased shares resulting from the reverse stock split. Initial Public Offering On November 13, 2017, the Company issued and sold 10,714,000 shares of its common stock at a price per share of $14.00 in its initial public offering (the “IPO”). The Company received net proceeds of $137.2 million after deducting underwriting discounts and commissions of $10.5 million and offering costs of $2.3 million. Deferred issuance costs of $783,695 have been incurred and are recognized as other current assets in the September 30, 2017 condensed consolidated balance sheet, of which $570,218 had been paid, as of September 30, 2017. In addition, on December 13, 2017, the Company issued and sold an additional 981,107 shares of its common stock at the initial public offering price of $14.00 per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, which resulted in net proceeds of approximately $12.8 million, after underwriting discounts and commissions of $1.0 million. Automatic Conversion of Preferred Stock On November 13, 2017, upon the closing of the Company’s IPO, all outstanding shares of the Company’s convertible preferred stock converted into 30,070,034 shares of the Company’s common stock. Fair Value of Financial Instruments Management believes that the carrying amounts of the Company’s financial instruments, including accounts payable and accrued expenses, approximate the fair value due to the short-term nature of those instruments. The Company follows the fair value hierarchy within Accounting Standards Codification (“ASC”) 820, Fair Value Measurements, and classifies its financial instruments as Level I. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) In February 2016, the FASB issued ASU 2016-02, Leases

Convertible Preferred Stock

Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Convertible Preferred Stock	3. Convertible Preferred Stock Series E Convertible Preferred Stock In August 2017, the Company issued and sold 7,792,035 shares of series E convertible preferred stock at $2.571 per share for aggregate proceeds of $20,033,322, less issuance costs of $285,475. Upon closing of the Company’s initial public offering on November 13, 2017, all shares of convertible preferred stock converted into shares of common stock.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Accrued Expenses Text Block	4. Accrued Expenses Accrued expenses are as follows: December 31, March 31, 2017 2018 Accrued research and development $ 2,463,808 $ 1,857,970 Accrued payroll liabilities 251,491 $ 703,186 Other 175,406 $ 148,645 Total $ 2,890,705 $ 2,709,801

Long-term Debt

Long-term Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-term Debt	5. Long term Debt Term Loan Facility On October 20, 2017, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”) to provide for a $20.0 million term loan facility (the “term loan facility”). Borrowings under the term loan facility bear interest at a floating rate per annum equal to the WSJ prime rate plus 1.50%; provided, however, that in an event of default, as defined in the loan and security agreement, the interest rate applicable to borrowings under such agreement will be increased by 5.0%. Under the agreement, the Company is required to make monthly interest-only payments through November 1, 2019 and is required to make 24 equal monthly payments of principal, plus accrued interest, from November 1, 2019 through October 1, 2021, when all unpaid principal and interest becomes due and payable. The Company may voluntarily prepay all, but not less than all, of the outstanding principal at any time prior to the maturity date, subject to a prepayment fee, which ranges from 0% to 2% of the outstanding principal. A final payment of $1.6 million is due upon the earlier to occur of the maturity of the loan, the acceleration or prepayment of all outstanding principal or the termination of the term loan facility. Borrowings under the term loan facility are secured by a first priority lien on all of the Company’s assets, excluding intellectual property owned by the Company. The Company has agreed to a negative pledge on its intellectual property and to grant a security interest on its interest in its licenses from the University of Pennsylvania (“Penn”) if Penn consents to such security interest. The term loan facility contains customary events of default and affirmative and negative covenants, including restrictions on the Company’s ability to pay dividends and incur additional debt, but does not contain any financial covenants. In connection with the Company’s entry into the term loan facility, the Company issued to SVB a warrant to purchase 14,064 shares of the Company’s common stock with an exercise price per share of $5.484. The warrant has a ten-year term and includes a put option pursuant to which, in the event of an acquisition, change in control or dissolution or winding up of the Company, or the expiration of the warrant, SVB may require the Company to repurchase the warrant for a total aggregate purchase price of $250,000. Related Party Promissory Note On October 19, 2017, the Company issued and sold an unsecured promissory note in the principal amount of $7.0 million to Golda Darty Partners S.A. (“GDP”), an affiliate of one of the Company’s stockholders. The promissory note bears interest at a rate per annum of 8.0%, and is due and payable quarterly in arrears on the 19th day of each April, July, October and January beginning on January 19, 2018. The promissory note has a maturity date of October 19, 2022. The promissory note is contractually subordinated to the term loan facility with SVB. In connection with the issuance and sale of the above promissory note, the Company issued to GDP a warrant to purchase 93,764 shares of the Company’s common stock at a price per share of $5.484, which was exercised in whole in October 2017. The Company recorded the fair value of the warrant in the aggregate amount of $430,160 as a discount to the promissory note. This amount is being accreted as additional interest expense over the term of the promissory note. The contractual maturities of our long term debt obligations due subsequent to March 31, 2018 are as follows: 2018 $ — 2019 1,666,667 2020 10,000,000 2021 8,333,333 2022 7,000,000 $ 27,000,000

Refundable Research and Develop

Refundable Research and Development Credit and Income Taxes	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Refundable Research And Development Credit And Income Taxes	6. Refundable Research and Development Credit and Income Taxes The Company earns non-income related refundable Australian research and development credits that are settled and paid to the Company annually. The associated income from the credits are an offset to research and development expenses. The Company’s income tax provision is computed based on the federal statutory rate and the average state statutory rates, net of the related federal benefit. For the three months ended March 31, 2018 and 2017, there were no current or deferred income tax expenses or benefits due to the Company’s, net losses, research and development credits and increases in its deferred tax asset valuation allowance during those periods. Under Section 382 of the Internal Revenue Code, as amended (“Section 382”), the Company’s net operating loss carryforwards (“NOLs”) and other deferred tax assets can generally be used to offset future taxable income and therefore reduce federal income tax obligations. However, the Company's ability to use its NOLs would be limited if there was an “ownership change” as defined by Section 382. This would occur if shareholders owning (or deemed to own under the tax rules) 5% or more of the Company's voting and non-voting common shares increase their aggregate ownership of the Company by more than 50 percentage points over a defined period of time. The company had an ownership change on September 8, 2015. Therefore, a portion of the NOL and tax credit carryforwards are subject to an annual utilization limitation. The deferred tax asset includes approximately $36,181,012 of tax affected net operating loss carryforwards and $9,553,510 of research and development tax credit carryforwards. Of the $36,181,012 tax affected net operating loss, $12,303,415 is limited under IRC Sec. 382. Of the $9,553,510 tax credit carryforwards, $1,892,390 is limited under IRC Sec. 383. Subsequent ownership changes may further affect the limitation in future years. The Company’s estimate of the realizability of the deferred tax asset is dependent on estimates of projected future levels of taxable income. In analyzing future taxable income levels, the Company considered all evidence currently available, both positive and negative. Based on this analysis, the Company has recorded a valuation allowance for all deferred tax assets as of March 31, 2018. Tax Act Enactment During the fourth quarter of 2017, the Company accounted for the estimated impacts of the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) including the re-measurement of the Company’s deferred tax assets and liabilities, which resulted in a total impact of $16.0 million to the gross deferred tax balance. As there is a valuation allowance recorded for all deferred tax assets as of March 31, 2018, there was no impact to the net deferred tax assets balance. The Company was not subject to the one-time mandatory transition tax on cumulative foreign subsidiary earnings as the Company has a net cumulative deficit in earnings and profits from foreign subsidiaries. The estimated impacts of the Tax Act recorded through March 31, 2018 are provisional in nature, and the Company will continue to assess the impact that various provisions of the Tax Act will have on its business.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies The Company contracts to conduct research and development activities with remaining contract costs of approximately $1,915,000 at March 31, 2018, that will be incurred in future periods. The scope of the services under the research and development contracts can be modified and the contracts cancelled by the Company upon written notice. In some instances, the contracts may be cancelled by the third party upon written notice.

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net Loss per Share	8. Net Loss per Share Since the Company was in a loss position for all periods presented, basic net loss per common share is the same as diluted net loss per common share for all periods presented as the inclusion of all potential common shares outstanding would have been anti-dilutive. Shares outstanding presented below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, as their effect is anti-dilutive: For the Three Months Ended March 31, 2017 2018 Convertible preferred stock 56,347,420 — Common stock options 8,697,028 7,418,316 Common stock warrants — 14,064 Total 65,044,448 7,432,380

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	9. Subsequent Events On April 23, 2018, the Company issued and sold 5,500,000 shares of its common stock at a price per share of $25.50 in the 2018 follow-on offering. The Company received net proceeds of $131.3 million after deducting underwriting discounts and commissions of $8.4 million and estimated offering costs of $0.5 million. Deferred issuance costs of $194,347 have been incurred and are recognized as other current assets in the March 31, 2018 condensed consolidated balance sheet of which $2,664 have been paid as of March 31, 2018. The Company has granted to its underwriters an option, exercisable for 30 days from the date of the prospectus for the 2018 follow-on offering, to purchase up to 825,000 additional shares of the Company’s common stock at the public offering price of $25.50 per share, less the underwriting discount.

Summary of Significant Accounti

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Apellis Australia Pty Ltd. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and, accordingly, the balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of the Company’s financial information. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 19, 2018.
Reverse Stock Split	Reverse Stock Split On October 27, 2017, the Company effectuated a l-for-2.133 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on October 27, 2017. The reverse stock split resulted in an adjustment to the conversion prices of its convertible preferred stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying unaudited condensed consolidated financial statements and notes to the financial statements give retroactive effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders’ deficit reflects the reverse stock split by reclassifying from “common stock” to “additional paid-in capital” in an amount equal to the par value of the decreased shares resulting from the reverse stock split.
Initial Public Offering	Initial Public Offering On November 13, 2017, the Company issued and sold 10,714,000 shares of its common stock at a price per share of $14.00 in its initial public offering (the “IPO”). The Company received net proceeds of $137.2 million after deducting underwriting discounts and commissions of $10.5 million and offering costs of $2.3 million. Deferred issuance costs of $783,695 have been incurred and are recognized as other current assets in the September 30, 2017 condensed consolidated balance sheet, of which $570,218 had been paid, as of September 30, 2017. In addition, on December 13, 2017, the Company issued and sold an additional 981,107 shares of its common stock at the initial public offering price of $14.00 per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, which resulted in net proceeds of approximately $12.8 million, after underwriting discounts and commissions of $1.0 million.
Automatic Conversion of Preferred Stock	Automatic Conversion of Preferred Stock On November 13, 2017, upon the closing of the Company’s IPO, all outstanding shares of the Company’s convertible preferred stock converted into 30,070,034 shares of the Company’s common stock.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Management believes that the carrying amounts of the Company’s financial instruments, including accounts payable and accrued expenses, approximate the fair value due to the short-term nature of those instruments. The Company follows the fair value hierarchy within Accounting Standards Codification (“ASC”) 820, Fair Value Measurements, and classifies its financial instruments as Level I.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) In February 2016, the FASB issued ASU 2016-02, Leases

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2018
Text Block [Abstract]
Schedule of Accrued Expenses	Accrued expenses are as follows: December 31, March 31, 2017 2018 Accrued research and development $ 2,463,808 $ 1,857,970 Accrued payroll liabilities 251,491 $ 703,186 Other 175,406 $ 148,645 Total $ 2,890,705 $ 2,709,801

Long-term Debt (Tables)

Long-term Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Summary of Contractual Maturities of Long-term Debt Obligations	The contractual maturities of our long term debt obligations due subsequent to March 31, 2018 are as follows: 2018 $ — 2019 1,666,667 2020 10,000,000 2021 8,333,333 2022 7,000,000 $ 27,000,000

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Summary of Shares Outstanding that were Excluded from Calculation of Diluted Net Loss Per Share	Shares outstanding presented below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, as their effect is anti-dilutive: For the Three Months Ended March 31, 2017 2018 Convertible preferred stock 56,347,420 — Common stock options 8,697,028 7,418,316 Common stock warrants — 14,064 Total 65,044,448 7,432,380

Nature of Organization and Op20

Nature of Organization and Operations - Additional Information (Detail) - USD ($)	Apr. 23, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Cash and cash equivalents		$ 152,930,977	$ 175,643,529	$ 16,436,538	$ 24,863,488
Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from follow on offering after deducting underwriting discounts and commissions	$ 131,300,000

Basis of Presentation - Additio

Basis of Presentation - Additional Information (Detail)	Dec. 13, 2017USD ($)$ / sharesshares	Nov. 13, 2017USD ($)$ / sharesshares	Oct. 27, 2017$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2017$ / shares
Summary Of Significant Accounting Policies [Line Items]
Description of common stock reverse stock split				The Company effectuated a l-for-2.133 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on October 27, 2017.
Common stock reverse stock split, conversion ratio			0.468823254
Common stock, par value | $ / shares			$ 0.0001	$ 0.0001	$ 0.0001
Reverse stock split, effective date			Oct. 27, 2017
Deferred issuance costs				$ 194,347
Payment of issuance costs				$ 2,664
Conversion of preferred stock to common stock | shares		30,070,034
IPO [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of additional shares issued and sold | shares	981,107	10,714,000
Public offering price of common stock | $ / shares	$ 14	$ 14
Proceeds from initial offering after deducting underwriting discounts and commissions	$ 12,800,000	$ 137,200,000
Underwriting discounts and commissions	$ 1,000,000	10,500,000
Initial public offering costs		2,300,000
Deferred issuance costs		783,695
Payment of issuance costs		$ 570,218

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Aug. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Convertible preferred stock issued and sold		0	0
Preferred stock, par value		$ 0.0001	$ 0.0001
Stock issuance costs		$ 2,664
Series E Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Convertible preferred stock issued and sold	7,792,035
Preferred stock, par value	$ 2.571
Gross proceeds from issuance and sale of convertible preferred stock	$ 20,033,322
Stock issuance costs	$ 285,475

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Accrued research and development	$ 1,857,970	$ 2,463,808
Accrued payroll liabilities	703,186	251,491
Other	148,645	175,406
Total	$ 2,709,801	$ 2,890,705

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail)	Oct. 20, 2017USD ($)Installment$ / sharesshares	Oct. 19, 2017USD ($)$ / sharesshares	Mar. 31, 2018
Unsecured Promissory Note | Golda Darty Partners S A [Member]
Debt Instrument [Line Items]
Debt instrument, due and payment description			The promissory note bears interest at a rate per annum of 8.0%, and is due and payable quarterly in arrears on the 19th day of each April, July, October and January beginning on January 19, 2018.
Warrant to purchase common stock | shares		93,764
Exercise price per share | $ / shares		$ 5.484
Principal amount		$ 7,000,000
Interest rate		8.00%
Maturity date		Oct. 19, 2022
Fair value of warrant		$ 430,160
Term Loan Facility [Member]
Debt Instrument [Line Items]
Final payment due amount	$ 1,600,000
Term Loan Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Prepayment fee, percentage	0.00%
Term Loan Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Prepayment fee, percentage	2.00%
Silicon Valley Bank [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Warrant to purchase common stock | shares	14,064
Exercise price per share | $ / shares	$ 5.484
Warrant term	10 years
Aggregate purchase price	$ 250,000
Loan and Security Agreement [Member] | Silicon Valley Bank [Member]
Debt Instrument [Line Items]
Term loan facility	$ 20,000,000
Increase in interest rate	5.00%
Debt instrument, due and payment description			The Company is required to make monthly interest-only payments through November 1, 2019 and is required to make 24 equal monthly payments of principal, plus accrued interest, from November 1, 2019 through October 1, 2021, when all unpaid principal and interest becomes due and payable
Loan and Security Agreement [Member] | Silicon Valley Bank [Member] | Convertible Preferred Stock [Member]
Debt Instrument [Line Items]
Debt instrument, number of equal monthly installments | Installment	24
Loan and Security Agreement [Member] | Silicon Valley Bank [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Interest bear rate	1.50%

Long-term Debt - Summary of Con

Long-term Debt - Summary of Contractual Maturities of Long-term Debt Obligations (Detail)	Mar. 31, 2018USD ($)
Debt Disclosure [Abstract]
2,019	$ 1,666,667
2,020	10,000,000
2,021	8,333,333
2,022	7,000,000
Long-term Debt	$ 27,000,000

Refundable Research and Devel26

Refundable Research and Development Credit and Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Refundable Research Development And Income Taxes [Line Items]
Current income tax expense or benefits	$ 0		$ 0
Deferred income tax expense or benefits	0		$ 0
Deferred tax assets affected net operating loss carryforwards	36,181,012
Research and development tax credit carryforwards	9,553,510
Gross deferred tax balance		$ 16,000,000
IRC Sec. 382 [Member]
Refundable Research Development And Income Taxes [Line Items]
Deferred tax assets affected net operating loss carryforwards	12,303,415
IRC Sec. 383 [Member]
Refundable Research Development And Income Taxes [Line Items]
Research and development tax credit carryforwards	$ 1,892,390

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Mar. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Remaining contract costs	$ 1,915,000

Net Loss per Share - Summary of

Net Loss per Share - Summary of Shares Outstanding that were Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	7,432,380	65,044,448
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount		56,347,420
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	7,418,316	8,697,028
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	14,064

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Apr. 23, 2018	Mar. 31, 2018
Subsequent Event [Line Items]
Deferred issuance costs		$ 194,347
Payment of issuance costs		$ 2,664
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of additional shares issued and sold	5,500,000
Common stock price per share	$ 25.50
Proceeds from follow on offering after deducting underwriting discounts and commissions	$ 131,300,000
Underwriting discounts and commissions	8,400,000
Estimated offering costs	$ 500,000
Subsequent Event [Member] | Underwriters [Member]
Subsequent Event [Line Items]
Option exercisable period from date of prospectus	30 days
Maximum number of additional shares granted under purchase option	825,000