Pandion Therapeutics 10-Q 31 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 31, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-39381
Entity Registrant Name	PANDION THERAPEUTICS, INC.
Entity Central Index Key	0001807901
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-3015614
Entity Address, Address Line One	134 Coolidge Avenue
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	617
Local Phone Number	393-5925
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	PAND
Security Exchange Name	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		29,519,902

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 105,725	$ 15,970
Accounts receivable	1,318	1,035
Prepaid expenses and other current assets	3,377	2,960
Total current assets	110,420	19,965
Property and equipment, net	2,592	1,054
Restricted cash	502
Total assets	113,514	21,019
Current liabilities:
Accounts payable	3,742	1,207
Accrued expenses and other current liabilities	2,260	1,455
SAFE agreement	6,000
Current portion of deferred revenue	4,748	4,365
Total current liabilities	16,750	7,027
Deferred revenue, net of current portion	4,582	6,053
Long-term debt, net of issuance costs	1,815	3,676
Other long-term liabilities	253	85
Total liabilities	23,400	16,841
Commitments and contingencies (Note 7)
Redeemable convertible preferred shares, no par value; 91,534,629 and 51,217,321 shares authorized at June 30, 2020 and December 31, 2019, respectively; 91,441,336 and 35,524,212 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively; liquidation value of $152,596 at June 30, 2020	152,596	46,967
Members’ deficit
Incentive shares, no par value; 13,182,678 and 7,717,678 shares authorized at June 30, 2020 and December 31, 2019, respectively; 2,364,595 and 946,751 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	382	172
Accumulated deficit	(62,864)	(42,961)
Total members’ deficit	(62,482)	(42,789)
Total liabilities, redeemable convertible preferred shares and members’ deficit	$ 113,514	$ 21,019

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Redeemable convertible preferred shares, par value	$ 0	$ 0
Redeemable convertible preferred shares, shares authorized	91,534,629	51,217,321
Redeemable convertible preferred shares, shares issued	91,441,336	35,524,212
Redeemable convertible preferred shares, shares outstanding	91,441,336	35,524,212
Redeemable convertible preferred shares, liquidation value	$ 152,596
Common shares, no par value	$ 0	$ 0
Common shares, authorized	100,000,000	62,000,000
Common shares, Issued	1,237,639	1,237,639
Common shares, outstanding	1,195,794	1,110,767
Incentive shares no par value	$ 0	$ 0
Incentive shares, authorized	13,182,678	7,717,678
Incentive shares, issued	2,364,595	946,751
Incentive shares, outstanding	2,364,595	946,751

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue	$ 1,955		$ 3,956
Operating expenses
Research and development	8,860	$ 4,934	15,802	$ 10,019
General and administrative	2,297	840	3,863	1,614
Total operating expenses	11,157	5,774	19,665	11,633
Loss from operations	(9,202)	(5,774)	(15,709)	(11,633)
Interest income	4	89	45	143
Interest expense	(39)		(82)
Fair value adjustments to convertible note			89
Net loss	(9,237)	(5,685)	(15,657)	(11,490)
Change in redemption value of redeemable convertible preferred shares	(2,712)	(982)	(4,245)	(1,936)
Net loss attributable to common shares – basic and diluted	$ (11,949)	$ (6,667)	$ (19,902)	$ (13,426)
Net loss per common share, basic and diluted	$ (10.15)	$ (6.30)	$ (17.23)	$ (13.19)
Weighted-average number of shares outstanding used in computing net loss per common share, basic and diluted	1,177,479	1,057,617	1,154,856	1,018,254

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Shares and Members' Deficit (Unaudited) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Beginning balance			$ (50,683)	$ (42,789)	$ (23,807)	$ (17,057)	$ (42,789)	$ (17,057)	$ (17,057)
Beginning balance (in shares)			71,324,468	35,524,212	35,524,212		35,524,212
Beginning balance			$ 108,020	$ 46,967	$ 43,897		$ 46,967
Issuance of Series A redeemable convertible preferred shares, net of issuance costs			$ 41,864	$ 17,980		$ 17,966
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)			20,116,868	15,693,109		15,693,109
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note				$ 1,811
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note (in shares)				948,225
Issuance of Series B redeemable convertible preferred shares, net of issuance costs		$ 80,000		$ 39,728
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)	19,158,922	19,158,922		19,158,922
Accretion of redeemable convertible preferred shares to redemption value			$ 2,712	$ 1,534	982	$ 954
Accretion of redeemable convertible preferred shares to redemption value			(2,712)	(1,534)	(982)	(954)
Issuance of incentive shares			150	60	11	9
Net loss			(9,237)	(6,420)	(5,685)	(5,805)	(15,657)	(11,490)	(21,900)
Ending balance	$ (62,482)	$ (50,683)	$ (62,482)	$ (50,683)	$ (30,463)	$ (23,807)	$ (62,482)	$ (30,463)	$ (42,789)
Ending balance (in shares)	91,441,336	71,324,468	91,441,336	71,324,468	35,524,212	35,524,212	91,441,336	35,524,212	35,524,212
Ending balance	$ 152,596	$ 108,020	$ 152,596	$ 108,020	$ 44,879	$ 43,897	$ 152,596	$ 44,879	$ 46,967
Redeemable Convertible Preferred Stock
Beginning balance (in shares)						19,831,103		19,831,103	19,831,103
Beginning balance						$ 24,977		$ 24,977	$ 24,977
Reorganization (in shares)						(19,831,103)
Reorganization						$ (24,977)
Redeemable Convertible Preferred Shares
Beginning balance
Beginning balance (in shares)			71,324,468	35,524,212	35,524,212		35,524,212
Beginning balance			$ 108,020	$ 46,967	$ 43,897		$ 46,967
Reorganization (in shares)						19,831,103
Reorganization						$ 24,977
Issuance of Series A redeemable convertible preferred shares, net of issuance costs				$ 17,980		$ 17,966
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)				15,693,109		15,693,109
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note				$ 1,811
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note (in shares)				948,225
Issuance of Series B redeemable convertible preferred shares, net of issuance costs			$ 41,864	$ 39,728
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)			20,116,868	19,158,922
Accretion of redeemable convertible preferred shares to redemption value			$ 2,712	$ 1,534	$ 982	$ 954
Ending balance	$ 152,596		$ 152,596				$ 152,596
Ending balance (in shares)	91,441,336	71,324,468	91,441,336	71,324,468	35,524,212	35,524,212	91,441,336	35,524,212	35,524,212
Ending balance		$ 108,020		$ 108,020	$ 44,879	$ 43,897		$ 44,879	$ 46,967
Common Stock
Beginning balance (in shares)						940,713		940,713	940,713
Reorganization (in shares)						(940,713)
Common Shares
Beginning balance (in shares)			1,165,537	1,110,767	1,019,996		1,110,767
Reorganization (in shares)						940,713
Vesting of restricted common shares			30,257	54,770	79,283	79,283
Ending balance (in shares)	1,195,794	1,165,537	1,195,794	1,165,537	1,099,279	1,019,996	1,195,794	1,099,279	1,110,767
Incentive Shares
Beginning balance			$ 232	$ 172	$ 61		$ 172
Beginning balance (in shares)			946,751	946,751	230,968		946,751
Reorganization						$ 52
Issuance of incentive shares			$ 150	$ 60	$ 11	$ 9
Issuance of incentive shares (in shares)			1,417,844		66,532	230,968
Ending balance	$ 382	$ 232	$ 382	$ 232	$ 72	$ 61	$ 382	$ 72	$ 172
Ending balance (in shares)	2,364,595	946,751	2,364,595	946,751	297,500	230,968	2,364,595	297,500	946,751
Additional Paid-In Capital
Beginning balance						$ 52		$ 52	$ 52
Reorganization						(52)
Accumulated Deficit
Beginning balance			$ (50,915)	$ (42,961)	$ (23,868)	(17,109)	$ (42,961)	(17,109)	(17,109)
Accretion of redeemable convertible preferred shares to redemption value			(2,712)	(1,534)	(982)	(954)
Net loss			(9,237)	(6,420)	(5,685)	(5,805)
Ending balance	$ (62,864)	$ (50,915)	$ (62,864)	$ (50,915)	$ (30,535)	$ (23,868)	$ (62,864)	$ (30,535)	$ (42,961)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Shares and Members' Deficit (Unaudited) (Parenthetical) - USD ($)	1 Months Ended		3 Months Ended			6 Months Ended
	Mar. 31, 2020	Jan. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Series A Redeemable Convertible Preferred Shares
Shares issuance costs net		$ 34,000		$ 20,000	$ 34,000	$ 20,000	$ 33,000
Series B Redeemable Convertible Preferred Shares
Shares issuance costs net	$ 271,000		$ 136,000	$ 271,000		$ 407,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($)	1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended
	Jan. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities
Net loss		$ (9,237,000)	$ (6,420,000)	$ (5,685,000)	$ (5,805,000)	$ (15,657,000)	$ (11,490,000)	$ (21,900,000)
Adjustment to reconcile net loss to net cash used in operating activities:
Depreciation expense						171,000	112,000
Equity-based compensation expense						210,000	20,000
Fair value adjustments on convertible notes						(89,000)
Noncash interest expense						39,000
Changes in operating assets and liabilities:
Accounts receivable						(283,000)
Prepaid expenses and other current assets						132,000	518,000
Accounts payable						1,630,000	103,000
Accrued expenses and other current liabilities						847,000	(886,000)
Deferred revenue						(1,088,000)
Net cash used in operating activities						(14,088,000)	(11,623,000)
Cash flows from investing activities
Purchases of property and equipment						(1,228,000)	(437,000)
Net cash used in investing activities						(1,228,000)	(437,000)
Cash flows from financing activities
Proceeds from simple agreement for future equity						6,000,000
Net cash provided by financing activities						105,573,000	17,967,000
Net increase in cash and cash equivalents						90,257,000	5,907,000
Cash, cash equivalents and restricted cash, beginning of period	$ 10,172,000		15,970,000		10,172,000	15,970,000	10,172,000	10,172,000
Cash, cash equivalents and restricted cash, end of period		106,227,000		16,079,000		106,227,000	16,079,000	15,970,000
Components of cash, cash equivalents, and restricted cash
Cash and cash equivalents		105,725,000		$ 16,079,000		105,725,000	16,079,000	$ 15,970,000
Restricted cash		502,000				502,000
Supplemental cash flow disclosures:
Cash paid for interest						43,000
Supplemental disclosures of noncash activities:
Exchange of JDRF note and accrued interest for Series A redeemable convertible preferred shares						1,811,000
Deferred offering costs not yet paid						549,000
Purchase of property and equipment included in accounts payable						481,000
Series A Redeemable Convertible Preferred Shares
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares						18,000,000	18,000,000
Redeemable convertible preferred share issuance costs	$ (34,000)		(20,000)		$ (34,000)	(20,000)	$ (33,000)
Series B Redeemable Convertible Preferred Shares
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares						82,000,000
Redeemable convertible preferred share issuance costs		$ (136,000)	$ (271,000)			$ (407,000)

Description of Business, Organi

Description of Business, Organization and Liquidity	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business, Organization and Liquidity	1. Business Pandion Therapeutics Holdco LLC is a clinical stage biopharmaceutical company developing novel therapeutics designed to address the unmet needs of patients suffering from autoimmune diseases. We have combined a network-based conceptualization of the immune system with expertise in advanced protein engineering to develop our TALON (Therapeutic Autoimmune reguLatOry proteiN) drug design and discovery platform. As used in these financial statements, unless the context otherwise requires, references to the “company”, “we,” “us,” and “our” refer to Pandion Therapeutics Holdco LLC, its wholly owned subsidiaries Pandion Therapeutics, Inc. and Pandion Program Co 1, Inc., and Pandion Securities Corp., a subsidiary of Pandion Therapeutics, Inc. Pandion Therapeutics, Inc. was incorporated on September 19, 2016 as a Delaware corporation. We began operations in January 2017. Our principal offices are located in Watertown, Massachusetts. On December 31, 2018, Pandion Therapeutics Holdco LLC was formed in the state of Delaware. On January 1, 2019, we completed a series of transactions in which Pandion Therapeutics, Inc. became a direct wholly owned subsidiary of Pandion Therapeutics Holdco LLC and all outstanding equity securities of Pandion Therapeutics, Inc. were canceled and converted on a one-for-one basis into equity securities of Pandion Therapeutics Holdco LLC, which we refer to as the Restructuring. In accordance with the terms of the LLC Operating Agreement, and on the effective date of the Restructuring; • each share of Pandion Therapeutics, Inc. common stock issued and outstanding immediately prior to the effective date of the Restructuring was converted into one common share of Pandion Therapeutics Holdco LLC; • each share of Pandion Therapeutics, Inc. Series A redeemable convertible preferred stock issued and outstanding immediately prior to the effective date of the Restructuring was converted into one Series A redeemable convertible preferred share of Pandion Therapeutics Holdco LLC; • all outstanding stock options to purchase shares of Pandion Therapeutics, Inc. common stock were cancelled and replaced with the same number of incentive shares in Pandion Therapeutics Holdco LLC; • each warrant issued by Pandion Therapeutics, Inc. that was outstanding immediately prior to the effective date of the Restructuring was cancelled and an equivalent number of incentive shares of Pandion Therapeutics Holdco LLC were issued; and • Pandion Therapeutics, Inc. became a wholly owned subsidiary of Pandion Therapeutics Holdco LLC. We determined that the Restructuring lacked economic substance and was therefore accounted for in a manner consistent with a common control transaction. Similarly, as there was no change in fair value between shareholders, individually or as a class, we determined that the exchange of shares occurring in the Restructuring should be accounted for as a modification of the equity securities and presented as a reclassification of the components of equity. Initial Public Offering and Corporate Conversion As described in Note 14, in July 2020 we completed our initial public offering. In contemplation of the initial public offering, on July 10, 2020, our wholly owned subsidiary Pandion Therapeutics, Inc. changed its name to Pandion Operations, Inc. and we subsequently engaged in the following transactions, which we refer to collectively as the Conversion: • we converted from a Delaware limited liability company to a Delaware corporation by filing a certificate of conversion with the Secretary of State of the State of Delaware; and • we changed our name from Pandion Therapeutics Holdco LLC to Pandion Therapeutics, Inc. As part of the Conversion: • holders of Series A preferred shares of Pandion Therapeutics Holdco LLC received one share of Series A preferred stock of Pandion Therapeutics, Inc. for each Series A preferred share held immediately prior to the Conversion; • holders of Series A prime preferred shares of Pandion Therapeutics Holdco LLC received one share of Series A prime preferred stock of Pandion Therapeutics, Inc. for each Series A prime preferred share held immediately prior to the Conversion; • holders of Series B preferred shares of Pandion Therapeutics Holdco LLC received one share of Series B preferred stock of Pandion Therapeutics, Inc. for each Series B preferred share held immediately prior to the Conversion; • holders of common shares of Pandion Therapeutics Holdco LLC received one share of common stock of Pandion Therapeutics, Inc. for each common share held immediately prior to the Conversion; • holders of outstanding incentive shares in Pandion Therapeutics Holdco LLC, all of which were intended to constitute profits interests for U.S. federal income tax purposes, received a number of shares of common stock of Pandion Therapeutics, Inc. based upon a conversion price determined by our board of directors immediately prior to the Conversion. Of the shares of common stock issued in respect of incentive shares, 1,368,515 continue to be subject to vesting in accordance with the vesting schedule applicable to such incentive shares. Based on the determined fair value of $18.00 per common share, the incentive shares converted into an aggregate of 1,504,586 shares of our common stock, and we granted options to purchase an aggregate of 859,147 shares of our common stock. Following the Conversion, Pandion Therapeutics, Inc. held all property and assets of Pandion Therapeutics Holdco Therapeutics Holdco Therapeutics Holdco Therapeutics Holdco Liquidity Since inception, we have devoted substantially all our efforts to business planning, research and development, recruiting management and technical staff, and raising capital and have financed our operations primarily through the issuance of redeemable convertible preferred shares, debt financings, a simple agreement for future equity, or SAFE, and a collaboration. We are subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if our product development efforts are successful, it is uncertain when, if ever, we will realize significant revenue from product sales. We have evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about our ability to continue as a going concern within one year after the date the condensed consolidated financial statements are issued. As of June 30, 2020, we had an accumulated deficit of $62.9 million. We have incurred losses and negative cash flows from operations since inception, including net losses of $15.7 million and $21.9 million for the six months ended June 30, 2020 and for the year ended December 31, 2019, respectively. We expect that our operating losses and negative cash flows will continue for the foreseeable future as we continue to develop our product candidates. We currently expect that our cash and cash equivalents of $105.7 million as of June 30, 2020 together with the net proceeds from our IPO, after deducting underwriting discounts and commissions but before deducting offering costs, of $142.2 million in July and August 2020, will be sufficient to fund our operating expenses and capital requirements for more than 12 months from the date the condensed consolidated financial statements are issued. However, additional funding will be necessary to fund future clinical and pre-clinical activities Coronavirus Pandemic In March 2020, the World Health Organization declared the global novel coronavirus disease 2019, or COVID-19, outbreak a pandemic. Our operations have not been significantly impacted by the COVID-19 pandemic. However, we cannot at this time predict the specific extent, duration, or full impact that the COVID-19 pandemic will have on our financial condition and operations, including ongoing and planned clinical trials. The impact of the COVID-19 pandemic on our financial performance will depend on future developments, including the duration and spread of the pandemic and related governmental advisories and restrictions. These developments and the impact of the COVID-19 pandemic on the financial markets and the overall economy are highly uncertain and cannot be predicted. If the financial markets and/or the overall economy are impacted for an extended period, our results may be materially adversely affected. On March 27, 2020, the United States enacted the Coronavirus Aid, Relief and Economic Security Act, or CARES Act. The Cares Act is an emergency economic stimulus package that includes spending and tax breaks to strengthen the United States economy and fund a nationwide effort to curtail the effect of the COVID-19 pandemic. The CARES Act provides sweeping tax changes in response to the COVID-19 pandemic, some of the more significant provisions include removal of certain limitations on utilization of net operating losses, increasing the loss carryback period for certain losses to five years, increasing the ability to deduct interest expense, and deferring social security payments, as well as amending certain provisions of the previously enacted Tax Cuts and Jobs Act. We do not believe the CARES Act will have a material impact on our financial position and results of operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES There have been no changes to the significant accounting policies as disclosed in Note 2 to our annual consolidated financial statements for the year ended December 31, 2019 included in our final prospectus for our IPO filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on July 17, 2020. Deferred Offering Costs We capitalize certain legal, accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. Upon the closing of our initial public offering, these costs will be reclassified to additional paid-in capital. If the equity financing is no longer considered probable of being consummated, the deferred offering costs would be expensed immediately to operating expenses in the statement of operations. There were $2.3 million of deferred offering costs capitalized at June 30, 2020 and no deferred offering costs at December 31, 2019. Unaudited Financial Information Our condensed consolidated financial statements included herein have been prepared in conformity with accounting principles generally accepted in the United States of America, or GAAP, and pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC. In our opinion, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. We consider events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. FAIR VALUE MEASUREMENTS The following tables present information about our financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): As of June 30, 2020 Total Level 1 Level 2 Level 3 Assets—money market funds $ 55,225 $ 55,225 $ — $ — Total financial assets measured at fair value $ 55,225 $ 55,225 $ — $ — Liabilities—SAFE $ 6,000 $ — $ — $ 6,000 Total financial liabilities measured at fair value $ 6,000 $ — $ — $ 6,000 As of December 31, 2019 Total Level 1 Level 2 Level 3 Assets—money market funds $ 3,517 $ 3,517 $ — $ — Total financial assets measured at fair value $ 3,517 $ 3,517 $ — $ — Liabilities—convertible note $ 1,900 $ — $ — $ 1,900 Total financial liabilities measured at fair value $ 1,900 $ — $ — $ 1,900 The following table presents a roll-forward of the fair value of the convertible note and SAFE for which fair value is determined by Level 3 inputs (in thousands): Six Months Ended June 30, 2020 2019 Balance at beginning of the period $ 1,900 $ 2,010 Fair value adjustment to convertible note (89 ) — Conversion of convertible note into Series A prime redeemable convertible preferred shares (1,811 ) — Initial fair value of SAFE 6,000 — Balance at end of the period $ 6,000 $ 2,010 Our money market funds are highly liquid investments that are valued based on quoted market prices in active markets, which represent a Level 1 measurement within the fair value hierarchy. Valuation techniques used to measure fair value maximize the use of relevant observable inputs and minimize the use of unobservable inputs. Our convertible note and SAFE is classified within Level 3 of the fair value hierarchy because the fair value measurement is based, in part, on significant inputs not observed in the market. The fair value of the SAFE on issuance was determined to be equal to the proceeds received. Fair value of the SAFE on conversion into common stock (Note 8) was determined to be equal to the fair value of the 333,333 common stock received of $6.0 million. Given the proximity of the conversion of the SAFE to the financial reporting period end, the fair value of the SAFE as of June 30, 2020 was also determined to be equal to the fair value of the common stock, of $6.0 million, received on conversion. In December 2018, we entered into an agreement for the sale of up to $4.0 million of convertible notes with the Juvenile Diabetes Research Foundation, or JDRF, T1D Fund, or JDRF Note, of which $2.0 million was initially sold. We have elected to account for the JDRF Note at fair value. We determine fair value of the JDRF Note using a scenario-based valuation method and a Monte Carlo simulation model with inputs based on certain subjective assumptions, including (a) expected stock price volatility, (b) calculation of a forecast horizon, (c) a risk-free interest rate, and (d) a discount rate. This approach results in the classification of these securities as Level 3 of the fair value hierarchy. The assumptions utilized to value the JDRF Note obligation as of December 31, 2019 were (a) expected stock price volatility of 90%; (b) a forecast horizon of 1.9 years: (c) a risk-free interest rate of 1.6%; and (d) a discount rate of 14.8%. For the year ended December 31, 2019, we recognized a $110,000 gain in the condensed consolidated statements of operations as fair value adjustments on convertible note with respect to changes to the fair value of the JDRF Note during the year. In February 2020, the outstanding principal and accrued interest under the JDRF Note automatically converted at a price of $2.294 per share into 948,225 Series A prime redeemable convertible preferred shares. The final fair value adjustment to the JDRF Note in the six months ended June 30, 2020 was determined to be equal to the fair value of the Series A prime redeemable convertible preferred shares into which the JDRF Note was converted. We determine the fair value of our Series A prime redeemable convertible preferred shares using a probability-weighted hybrid method combining (i) an option pricing model, or OPM, and (ii) an IPO scenario with reference to guideline IPOs in the biotechnology sector. For purposes of the OPM the key inputs include an 80.3% volatility rate, a 1.6-year estimated term, a risk-free rate of 0.3% and dividends of zero. For our IPO scenario, the key inputs include a weighted average cost of capital of 25% and a 0.8-year term to a liquidity event. For the six months ended June 30, 2020, we recognized a $89,000 gain in the condensed consolidated statements of operations as fair value adjustments on convertible note with respect to changes to the fair value of the JDRF Note. There were no transfers among Level 1, Level 2 or Level 3 categories in the six months ended June 30, 2020 and 2019.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid Expenses and Other Current Assets	4. PREPAID EXPENSES AND OTHER CURRENT ASSETS Prepaid expenses and other current assets consist of the following (in thousands): June 30, 2020 December 31, 2019 Loss recovery receivable $ — $ 1,875 Contract research 489 487 Tax receivable 163 334 Deferred offering costs 2,256 — Other 469 264 Total prepaid expenses and other current assets $ 3,377 $ 2,960 In October 2019, several batches of our drug substance were inadvertently disposed of by a vendor resulting in a loss of approximately $1.9 million for the year ended December 31, 2019. During the first quarter of 2020, we entered into a settlement agreement to recover the full cost of replacing the drug substance, resulting in a loss recovery receivable being recorded at December 31, 2019. We received the full loss recovery receivable during the six months ended June 30, 2020.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	5. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consist of the following (in thousands): June 30, 2020 December 31, 2019 Employee compensation costs $ 853 $ 915 Research and development costs 1,083 275 Professional costs 293 243 Other 31 22 Total accrued expenses and other current liabilities $ 2,260 $ 1,455

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Long-Term Debt	6. Long-term debt Convertible Note In February 2020, the outstanding principal and accrued interest under the JDRF Note automatically converted at an adjusted price of $2.294 per share into 948,225 Series A prime redeemable convertible preferred shares (Note 3). Term Loan In November 2019, we entered into a secured term loan facility

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. COMMITMENTS AND CONTINGENCIES We record a provision for contingent losses when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. As of June 30, 2020 and December 31, 2019, we had not recorded a provision for any contingent losses.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Shares	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Redeemable Convertible Preferred Shares	8. redeemable convertible preferred SHARES There have been no changes to the rights, preferences, privileges and restrictions of the redeemable convertible preferred shares as disclosed in Note 9 to our annual consolidated financial statements for the years ended December 31, 2019 and 2018 included in our final prospectus for our IPO filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on July 17, 2020. The following table summarizes outstanding redeemable convertible preferred shares (in thousands, except share and per share amounts): Series A Series A prime Series B Total Shares Amount Shares Amount Shares Amount Shares Amount Balance, January 1, 2019 — $ — — $ — — $ — — $ — Restructuring 19,831,103 24,977 — — — — 19,831,103 24,977 Issuance of Series A Preferred Shares, net of issuance costs of $34 15,693,109 17,966 — — — — 15,693,109 17,966 Accretion of redeemable convertible preferred shares to redemption value — 954 — — — — — 954 Balance, March 31, 2019 35,524,212 $ 43,897 — $ — — $ — 35,524,212 $ 43,897 Accretion of redeemable convertible preferred shares to redemption value — 982 — — — — — 982 Balance, June 30, 2019 35,524,212 $ 44,879 — $ — — $ — 35,524,212 $ 44,879 Balance, January 1, 2020 35,524,212 46,967 — — — — 35,524,212 46,967 Issuance of Series A Preferred Shares 15,693,109 17,980 — — — — 15,693,109 17,980 Issuance of Series A Prime Preferred Shares, on conversion of JDRF note — — 948,225 1,811 — — 948,225 1,811 Issuance of Series B Preferred Shares, net of issuance costs of $271 — — 19,158,922 39,728 19,158,922 39,728 Accretion of redeemable convertible preferred shares to redemption value — 1,193 — 3 — 338 — 1,534 Balance, March 31, 2020 51,217,321 $ 66,140 948,225 $ 1,814 19,158,922 $ 40,066 71,324,468 $ 108,020 Issuance of Series B Preferred Shares, net of issuance costs of $136 — — 20,116,868 41,864 20,116,868 41,864 Accretion of redeemable convertible preferred shares to redemption value — 1,465 — 45 — 1,202 — 2,712 Balance, June 30, 2020 51,217,321 $ 67,605 948,225 $ 1,859 39,275,790 $ 83,132 91,441,336 $ 152,596 In January 2019, we issued 15,693,109 Series A redeemable convertible preferred shares at a price of $1.147 per share for gross cash proceeds of $18.0 million and incurred issuance costs of $34,000. In February 2020, we issued 15,693,109 Series A redeemable convertible preferred shares at a price of $1.147 per share for gross cash proceeds of $18.0 million. At this closing, the outstanding principal and accrued interest under the JDRF Note automatically converted at a price of $2.294 per share into 948,225 Series A prime redeemable convertible preferred shares. In March 2020, we completed an $80.0 million Series B financing comprised of an initial closing and issuance of 19,158,922 Series B redeemable convertible preferred shares at $2.0878 per share to new and existing investors for gross cash proceeds of $40.0 million and incurred issuance costs of $271,000. In connection with the initial issuance of the Series B redeemable convertible preferred shares, the holders received the right to purchase, and we were under the obligation to sell, an additional 19,158,922 shares of Series B redeemable convertible preferred shares upon achieving a certain clinical development milestone, or the Tranche Right. We determined that the Tranche Right did not meet the definition of a freestanding financial instrument because it is not legally detachable. Further, we determined that the Tranche Right does not meet the definition of an embedded derivative that requires bifurcation from the equity instrument. Therefore, at the initial issuance of the Series B redeemable convertible preferred shares, there was no accounting for the Tranche Right. In June 2020, we issued 19,158,922 Series B redeemable convertible preferred shares at $2.0878 per share in a second closing of our Series B financing to existing investors for gross cash proceeds of $40.0 million and issued 957,946 Series B redeemable convertible preferred shares to JDRF per the terms of the JDRF Note for gross cash proceeds of $2.0 million. Simple Agreement for Future Equity In June 2020, we entered into a simple agreement for future equity, or SAFE, with a related party, pursuant to which we received $6.0 million in cash in exchange for the providing the investor the right to receive shares of our capital stock. The SAFE contained a number of conversion and redemption provisions, including settlement upon liquidity or dissolution events. We elected the fair value option of accounting for the SAFE. Upon consummation of our initial public offering in July 2020, the SAFE was converted, by its terms, into 333,333 shares of our common stock

Incentive Shares and Equity-Bas

Incentive Shares and Equity-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Incentive Shares and Equity-Based Compensation	9. INCENTIVE SHARES AND EQUITY-BASED COMPENSATION We granted profits interest awards to employees, consultants and non-employee members of our Board of Directors. The LLC Operating Agreement of Pandion Therapeutics Holdco LLC initially provided for the grant of up to 1,717,678 incentive shares, subject to certain restrictions as described below. Each unvested incentive share represented a non-voting equity interest in Pandion Therapeutics Holdco LLC that entitled the holder to a percentage of the profits and appreciation in the equity value of Pandion Therapeutics Holdco LLC arising after the date of grant and after such time as an applicable threshold amount was met. As part of the Restructuring (Note 1), all of the outstanding stock options and warrants issued under our 2017 Stock Incentive Plan were cancelled and exchanged for incentive shares. On January 1, 2019, we exchanged 195,630 stock options and 14,031 warrants for 209,661 incentive shares with a weighted average fair value of $0.66. We consider this exchange of awards to be a modification with no additional compensation expense. In March 2020, the LLC Operating Agreement was amended to authorize the issuance of up to an aggregate of 13,182,678 incentive shares. As of June 30, 2020, there were 10,818,083 incentive shares available for future grant. During the six months ended June 30, 2019, we granted 87,839 incentive shares with a weighted average fair value of $1.25 per share. During the six months ended June 30, 2020, we granted 1,417,844 incentive shares with a weighted average fair value of $2.01 per share. The fair value of incentive shares issued was determined using a Black-Scholes option pricing model with the following assumptions: Six Months Ended June 30, 2020 2019 Expected Term 2.0 1.2 Risk Free Rate 0.14% - 0.17% 1.96% - 2.60% Volatility 82.7% - 83.7% 71.5% - 72.3% Dividend Yield 0% 0% We recorded equity-based compensation expense related to the issuance of incentive shares of $210,000 and $20,000 during the six months ended June 30, 2020 and 2019, respectively, and $150,000 and $11,000 during the three months ended June 30, 2020 and 2019, respectively. As of June 30, 2020, there was $3.4 million of unrecognized compensation cost that is expected to be recognized over a weighted-average period of approximately 3.4 years. Equity-based compensation expense recorded in the accompanying condensed consolidated statements of operations is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 58 $ 5 $ 70 $ 9 General and administrative 92 6 140 11 Total equity-based compensation $ 150 $ 11 $ 210 $ 20

Astellas Agreement

Astellas Agreement	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Astellas Agreement	10. Astellas agreement In October 2019, we entered into a license and collaboration agreement, or the Astellas Agreement, with Astellas Pharma Inc., or Astellas, to develop locally acting immunomodulators for autoimmune diseases of the pancreas. Under the Astellas Agreement, we will be responsible for design and discovery of bispecific drug candidates based on our proprietary modular immune effector and tissue tether platform and Astellas will be responsible for conducting preclinical, clinical and commercialization activities for the selected candidates developed under the Astellas Agreement. In connection with our services to Astellas, we have granted a non-exclusive, non-transferable research license to Astellas and an exclusive, non-transferable, royalty-bearing, perpetual license to our technology with respect to the designated compound(s) for Astellas to further develop and ultimately commercialize for the treatment of autoimmune diseases of the pancreas. We do not share in the rights to clinical data and results under the Astellas Agreement. In addition, we are obligated under the Astellas Agreement to certain governance activities, reporting obligations and have made other ancillary commitments. The Astellas Agreement has a contractual term of five years. We identified our research and development services, the licenses granted to Astellas and our governance obligations to Astellas as the material promises under the Astellas Agreement. For purposes of identifying our performance obligations under the Astellas Agreement, we believe that while the licenses were granted to Astellas at the outset of the Astellas Agreement, the grant of those licenses did not singularly result in the transfer of our broader obligation to Astellas under the Astellas Agreement, as the license has no true value without the performance of our research and development services, the technology transfer and joint steering committee participation. Our research and development work with respect to bispecific drug candidates are unique with respect to our proprietary knowledge and know how in the design of bispecific antibodies and coupling bispecific antibodies with effector molecules to modulate immune activity. While capable of being distinct, those research and development activities are not distinct within the context of the Astellas Agreement. The licenses provided to Astellas are not transferable and we believe of limited value without our specific research and development services, and thus are not capable of being distinct. While our governance obligations are capable of being distinct, those activities are integrated with our research and development efforts under the Astellas Agreement and are not distinct in the context of the contract. Taken together with our research and development activities, including the governance oversight to those activities, the licenses granted under the Astellas Agreement will enable us to further advance designated licensed compounds into and through clinical development, regulatory approval and ultimately commercialization. Therefore, we believe the licenses bundled together with our research and development services and our governance obligations therein constitute a single distinct performance obligation under the Astellas Agreement for accounting purposes, or the Performance Obligation. Under the Astellas Agreement, we received a non-refundable, upfront payment of $10.0 million in November 2019. As of June 30, 2020, we estimate that we will receive a further $17.0 million of research funding and external cost reimbursement. We have the right to receive, on a licensed compound-by licensed compound basis, potential research and development milestone payments up to an aggregate of $43.0 million for the first Licensed Compound and $38.0 million for subsequent Licensed Compounds and regulatory milestones up to an aggregate of $105.0 million Provided Astellas designates at least one compound to progress in development under the Astellas Agreement, Astellas may designate up to five further compounds during a period of three years following the expiration of the five-year term of the Astellas Agreement for their further evaluation to progress towards development. We have no further obligation to Astellas during this period or in the evaluation of any such compounds they may designate. Astellas may request us to conduct services in connection with their evaluations, however we are not obligated to conduct such additional services. We assessed this provision as a potential material right and determined that we have no obligation to provide services (if requested) relating to the designated compounds during the additional period and, as such, this provision does not provide Astellas with a material right. While the contractual term under the Astellas Agreement is five years, based on the research plan and budget agreed to by the joint steering committee established under the Astellas Agreement, we initially estimate our research and development commitments will be completed by the end of 2022. As of June 30, 2020, we estimated a total transaction price of $29.9 million, consisting of the fixed upfront payment and estimated research funding and reimbursement of external costs of $19.9 million presently budgeted under the Astellas Agreement to be incurred through 2022, the effective term of our Performance Obligation to Astellas. Upon execution of the Astellas Agreement and as of June 30, 2020, contingent and variable consideration consisting of milestone payments has been constrained and excluded from the transaction price given the significant uncertainty of achievement of the development and regulatory milestones. We have allocated the transaction price entirely to the single, bundled performance obligation. We recorded the $10.0 million up-front payment from Astellas as deferred revenue in November 2019 and will record future invoices under the Astellas Agreement as deferred revenue. We will recognize the estimated total transaction price over the estimated period the research and development services are expected to be provided which, as of June 30, 2020, is through 2022. We believe the Performance Obligation is satisfied over the course of our performance of the research and development activities under the Astellas Agreement and, depicting our performance in satisfaction of the Performance Obligation, we use input method as a measure of progress towards completion of the Performance Obligation according to actual costs incurred compared to estimated total costs to estimate progress toward satisfaction of the Performance Obligation. We will remeasure our progress towards completion of the Performance Obligation at the end of each reporting period. For the three and six months ended June 30, 2020, we recognized $2.0 million and $4.0 million, respectively, of revenue under the Astellas Agreement. No revenue was recognized during the three and six months ended June 30, 2019. We invoice Astellas under the Astellas agreement quarterly in arrears for the cost of external services, quarterly in advance for our estimated internal services and annually to true-up our advance invoicing for estimated internal services. Invoiced amounts under the Astellas Agreement expected to be recognized as revenue within the 12 months following the balance sheet date are classified as a current portion of deferred revenue in the accompanying condensed consolidated balance sheets. Invoiced amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. As of June 30, 2020, we had no contract assets and short-term and long-term deferred revenues of $4.7 million and $4.6 million, respectively, which is presently estimated to be recognized through 2022. The aggregate amount of the transaction price allocated to the Performance Obligation that remains unsatisfied as of June 30, 2020 is estimated to be $25.0 million, of which we expect to recognize $7.6 million, $8.3 million and $9.1 million in the remainder of 2020, 2021 and 2022, respectively.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	11. INCOME TAXES We did not record a provision or benefit for income taxes during the six months ended June 30, 2020 and 2019. We continue to maintain a full valuation allowance against all of our deferred tax assets. We have evaluated the positive and negative evidence involving our ability to realize our deferred tax assets. We have considered our history of cumulative net losses incurred since inception and our lack of any commercially ready products. We have concluded that it is more likely than not that we will not realize the benefits of our deferred tax assets. We reevaluate the positive and negative evidence at each reporting period.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	12. net loss per share Net Loss Per Share Basic and diluted net loss per share attributable to common shareholders is calculated as follows (in thousands except share and per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Net loss $ (9,237 ) $ (5,685 ) $ (15,657 ) $ (11,490 ) Change in redemption value of redeemable convertible preferred shares (2,712 ) (982 ) (4,245 ) (1,936 ) Net loss attributable to common shares – basic and diluted $ (11,949 ) $ (6,667 ) $ (19,902 ) $ (13,426 ) Net loss per common share, basic and diluted $ (10.15 ) $ (6.30 ) $ (17.23 ) $ (13.19 ) Weighted-average number of shares outstanding used in computing net loss per common share, basic and diluted 1,177,479 1,057,617 1,154,856 1,018,254 The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Redeemable convertible preferred shares 91,441,336 35,524,212 91,441,336 35,524,212 Incentive shares 2,364,595 297,500 2,364,595 297,500 Warrants to purchase Series A redeemable convertible preferred shares 55,976 — 55,976 —

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	13. RELATED PARTY TRANSACTIONS We engage a firm managed by an executive of the company for professional services related to accounting, finance and other administrative functions. The costs incurred under this arrangement totaled $599,000 and $178,000 for the six months ended June 30, 2020 and 2019, respectively, and $364,000 and $97,000 for the three months ended June 30, 2020 and 2019, respectively, which were recorded as general and administrative expense in the accompanying condensed consolidated statements of operations. As of June 30, 2020 and December 31, 2019, amounts owed under this arrangement totaled approximately $95,000 and $34,000, respectively, and are included in accounts payable in the accompanying condensed consolidated balance sheets. We engaged a director of the company to provide advice and services as requested by the board of directors. The costs incurred under this arrangement totaled $63,000 and $75,000 for the six months ended June 30, 2020 and 2019, respectively, and $25,000 and $38,000 for the three months ended June 30, 2020 and 2019, respectively, which were recorded as general and administrative expense in the accompanying condensed consolidated statements of operations. As of June 30, 2020 and December 31, 2019, there were no amounts owed to the director under this arrangement. This agreement was terminated in July 2020. In March 2020, we issued 19,158,922 Series B preferred redeemable convertible shares at a price of $2.0878 per share, for gross cash proceeds of $40.0 million, of which 12,883,010 shares were sold to our 5% stockholders and their affiliates, executive officers and non-employee directors. In June 2020, we issued 19,158,922 Series B redeemable convertible preferred shares in an additional closing at the same price per share as the first closing for gross cash proceeds of $40.0 million, of which 12,883,010 shares were sold to our 5% stockholders and their affiliates, executive officers and non-employee directors.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	14. subsequent events 2020 Stock Incentive Plan In anticipation of our IPO, in July 2020, our board of directors adopted and our stockholders approved the 2020 Stock Incentive Plan (the “2020 Plan”), which became effective on July 16, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, awards of restricted stock, restricted stock units and other stock-based awards. The number of shares of our common stock reserved for issuance under the 2020 Plan is equal to the sum of: (1) 2,519,375; plus (2) the number of shares (up to 1,504,613) equal to the number of shares of common stock issued in respect of restricted common shares and incentive shares of Pandion Therapeutics Holdco LLC that are subject to vesting immediately prior to the effectiveness of the registration statement for our IPO that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by us at their original issuance price pursuant to a contractual repurchase right; plus (3) an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2021 and continuing until, and including, the fiscal year ending December 31, 2030, equal to the lowest of (i) 6,000,000 shares of our common stock, (ii) 4% of the number of shares of our common stock outstanding on such date and (iii) an amount determined by our board of directors. 2020 Employee Stock Purchase Plan In July 2020, our board of directors adopted and our stockholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective on July 16, 2020. A total of 209,948 shares of common stock were reserved for issuance under the ESPP. The number of shares of our common stock reserved for issuance under the ESPP will automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including, the fiscal year commencing on January 1, 2031, in an amount equal to the lowest of (1) 1,500,000 shares of our common stock, (2) 1% of the number of shares of our common stock outstanding on the first day of such fiscal year and (3) an amount determined by our board of directors. Reverse Share Split Our board of directors and shareholders approved a one-for-5.0994 reverse share split of our issued and outstanding common shares and incentive shares and a proportional adjustment to the existing conversion ratios for our preferred shares effective as of July 13, 2020. Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse share split. Initial Public Offering As described in Note 1, on July 16, 2020 and immediately prior to the effectiveness of the IPO, Pandion Therapeutics Holdco LLC converted from a Delaware limited liability company to a Delaware corporation by filing a certificate of conversion with the Secretary of State of the State of Delaware, and changed its name to Pandion Therapeutics, Inc. In the third quarter of 2020, we completed our IPO, selling an aggregate of 8,494,166 shares of common stock at a price to the public of $18.00 per share, which included 994,166 shares issued upon the partial exercise by the underwriters of their option to purchase additional shares of common stock in August 2020. We received net proceeds Immediately prior to consummation of the IPO, all outstanding shares of our Series A, Series A Prime and Series B convertible preferred stock were converted into 17,950,189 shares of common stock. Additionally, all of our outstanding incentive shares were converted into 1,504,586 shares of common stock. Upon the closing of the IPO On July 21, 2020, we amended and restated the certificate of incorporation of Pandion Therapeutics, Inc to authorize 200,000,000 shares of common stock and 5,000,000 shares of preferred stock, which shares of preferred stock are currently undesignated. Term Loan We repaid our Term Loan of $2.0 million in July 2020 as disclosed in Note 6.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Deferred Offering Costs	Deferred Offering Costs We capitalize certain legal, accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. Upon the closing of our initial public offering, these costs will be reclassified to additional paid-in capital. If the equity financing is no longer considered probable of being consummated, the deferred offering costs would be expensed immediately to operating expenses in the statement of operations. There were $2.3 million of deferred offering costs capitalized at June 30, 2020 and no deferred offering costs at December 31, 2019.
Unaudited Financial Information	Unaudited Financial Information Our condensed consolidated financial statements included herein have been prepared in conformity with accounting principles generally accepted in the United States of America, or GAAP, and pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC. In our opinion, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. We consider events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present information about our financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): As of June 30, 2020 Total Level 1 Level 2 Level 3 Assets—money market funds $ 55,225 $ 55,225 $ — $ — Total financial assets measured at fair value $ 55,225 $ 55,225 $ — $ — Liabilities—SAFE $ 6,000 $ — $ — $ 6,000 Total financial liabilities measured at fair value $ 6,000 $ — $ — $ 6,000 As of December 31, 2019 Total Level 1 Level 2 Level 3 Assets—money market funds $ 3,517 $ 3,517 $ — $ — Total financial assets measured at fair value $ 3,517 $ 3,517 $ — $ — Liabilities—convertible note $ 1,900 $ — $ — $ 1,900 Total financial liabilities measured at fair value $ 1,900 $ — $ — $ 1,900
Schedule of Fair Value of Convertible Note and SAFE for Which Fair Value Determined by Level 3 Inputs	The following table presents a roll-forward of the fair value of the convertible note and SAFE for which fair value is determined by Level 3 inputs (in thousands): Six Months Ended June 30, 2020 2019 Balance at beginning of the period $ 1,900 $ 2,010 Fair value adjustment to convertible note (89 ) — Conversion of convertible note into Series A prime redeemable convertible preferred shares (1,811 ) — Initial fair value of SAFE 6,000 — Balance at end of the period $ 6,000 $ 2,010

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Prepaid Expense And Other Assets Current [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): June 30, 2020 December 31, 2019 Loss recovery receivable $ — $ 1,875 Contract research 489 487 Tax receivable 163 334 Deferred offering costs 2,256 — Other 469 264 Total prepaid expenses and other current assets $ 3,377 $ 2,960

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): June 30, 2020 December 31, 2019 Employee compensation costs $ 853 $ 915 Research and development costs 1,083 275 Professional costs 293 243 Other 31 22 Total accrued expenses and other current liabilities $ 2,260 $ 1,455

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Shares (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Summary of Outstanding Redeemable Convertible Preferred Shares	The following table summarizes outstanding redeemable convertible preferred shares (in thousands, except share and per share amounts): Series A Series A prime Series B Total Shares Amount Shares Amount Shares Amount Shares Amount Balance, January 1, 2019 — $ — — $ — — $ — — $ — Restructuring 19,831,103 24,977 — — — — 19,831,103 24,977 Issuance of Series A Preferred Shares, net of issuance costs of $34 15,693,109 17,966 — — — — 15,693,109 17,966 Accretion of redeemable convertible preferred shares to redemption value — 954 — — — — — 954 Balance, March 31, 2019 35,524,212 $ 43,897 — $ — — $ — 35,524,212 $ 43,897 Accretion of redeemable convertible preferred shares to redemption value — 982 — — — — — 982 Balance, June 30, 2019 35,524,212 $ 44,879 — $ — — $ — 35,524,212 $ 44,879 Balance, January 1, 2020 35,524,212 46,967 — — — — 35,524,212 46,967 Issuance of Series A Preferred Shares 15,693,109 17,980 — — — — 15,693,109 17,980 Issuance of Series A Prime Preferred Shares, on conversion of JDRF note — — 948,225 1,811 — — 948,225 1,811 Issuance of Series B Preferred Shares, net of issuance costs of $271 — — 19,158,922 39,728 19,158,922 39,728 Accretion of redeemable convertible preferred shares to redemption value — 1,193 — 3 — 338 — 1,534 Balance, March 31, 2020 51,217,321 $ 66,140 948,225 $ 1,814 19,158,922 $ 40,066 71,324,468 $ 108,020 Issuance of Series B Preferred Shares, net of issuance costs of $136 — — 20,116,868 41,864 20,116,868 41,864 Accretion of redeemable convertible preferred shares to redemption value — 1,465 — 45 — 1,202 — 2,712 Balance, June 30, 2020 51,217,321 $ 67,605 948,225 $ 1,859 39,275,790 $ 83,132 91,441,336 $ 152,596

Incentive Shares and Equity-B_2

Incentive Shares and Equity-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Fair Value Assumptions of Incentive Shares Issued Determined Using Black-Scholes Option Pricing Model	The fair value of incentive shares issued was determined using a Black-Scholes option pricing model with the following assumptions: Six Months Ended June 30, 2020 2019 Expected Term 2.0 1.2 Risk Free Rate 0.14% - 0.17% 1.96% - 2.60% Volatility 82.7% - 83.7% 71.5% - 72.3% Dividend Yield 0% 0%
Summary of Equity-based Compensation Expense	Equity-based compensation expense recorded in the accompanying condensed consolidated statements of operations is as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 58 $ 5 $ 70 $ 9 General and administrative 92 6 140 11 Total equity-based compensation $ 150 $ 11 $ 210 $ 20

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss Per Share	Basic and diluted net loss per share attributable to common shareholders is calculated as follows (in thousands except share and per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Net loss $ (9,237 ) $ (5,685 ) $ (15,657 ) $ (11,490 ) Change in redemption value of redeemable convertible preferred shares (2,712 ) (982 ) (4,245 ) (1,936 ) Net loss attributable to common shares – basic and diluted $ (11,949 ) $ (6,667 ) $ (19,902 ) $ (13,426 ) Net loss per common share, basic and diluted $ (10.15 ) $ (6.30 ) $ (17.23 ) $ (13.19 ) Weighted-average number of shares outstanding used in computing net loss per common share, basic and diluted 1,177,479 1,057,617 1,154,856 1,018,254
Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss Per Share	The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Redeemable convertible preferred shares 91,441,336 35,524,212 91,441,336 35,524,212 Incentive shares 2,364,595 297,500 2,364,595 297,500 Warrants to purchase Series A redeemable convertible preferred shares 55,976 — 55,976 —

Description of Business, Orga_2

Description of Business, Organization and Liquidity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2019	Aug. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Description of Business, Organization and Liquidity [Line Items]
Entity incorporation date							Sep. 19, 2016
Conversion of stock description							On January 1, 2019, we completed a series of transactions in which Pandion Therapeutics, Inc. became a direct wholly owned subsidiary of Pandion Therapeutics Holdco LLC and all outstanding equity securities of Pandion Therapeutics, Inc. were canceled and converted on a one-for-one basis into equity securities of Pandion Therapeutics Holdco LLC, which we refer to as the Restructuring.
Shares converted	1
Shares issued	1
Common stock issued for incentive shares							1,368,515
Fair value per common share							$ 18
Incentive shares converted into common stock							1,504,586
Options granted to purchase common stock							859,147
Accumulated deficit			$ 62,864				$ 62,864		$ 42,961
Net losses and negative cash flows from operations			9,237	$ 6,420	$ 5,685	$ 5,805	15,657	$ 11,490	21,900
Cash and cash equivalents			$ 105,725		$ 16,079		$ 105,725	$ 16,079	$ 15,970
Loss carry back period under cares act							5 years
Subsequent Event
Description of Business, Organization and Liquidity [Line Items]
Net proceeds after deducting underwriting discounts and commissions but before deducting offering costs		$ 142,200

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Deferred offering costs capitalized	$ 2,256,000	$ 0

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets measured at fair value	$ 55,225	$ 3,517
Total financial liabilities measured at fair value	6,000	1,900
Convertible Note
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities measured at fair value		1,900
SAFE
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities measured at fair value	6,000
Level 1
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets measured at fair value	55,225	3,517
Level 3
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities measured at fair value	6,000	1,900
Level 3 | Convertible Note
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities measured at fair value		1,900
Level 3 | SAFE
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities measured at fair value	6,000
Money Market Funds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets measured at fair value	55,225	3,517
Money Market Funds | Level 1
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets measured at fair value	$ 55,225	$ 3,517

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Convertible Note and SAFE for Which Fair Value Determined by Level 3 Inputs (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Balance at beginning of the period	$ 1,900	$ 2,010
Fair value adjustment to convertible note	(89)
Conversion of convertible note into Series A prime redeemable convertible preferred shares	(1,811)
Initial fair value of SAFE	6,000
Balance at end of the period	$ 6,000	$ 2,010

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Jan. 01, 2019shares	Jun. 30, 2020USD ($)	Feb. 29, 2020$ / sharesshares	Jun. 30, 2020USD ($)shares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Proceeds from simple agreement for future equity				$ 6,000,000
Shares converted | shares	1
Fair value of assets transfers among Level 1 to Level 2		$ 0		0	$ 0
Fair value of assets transfers among Level 2 to Level 1		0		0	0
Fair value of liabilities transfers among Level 1 to Level 2		0		0	0
Fair value of liabilities transfers among Level 2 to Level 1		$ 0		0	0
Fair value of assets transfers into Level 3				0	0
Fair value of assets transfers out of Level 3				0	0
Fair value of liabilities transfers into Level 3				0	$ 0
Fair value of liabilities transfers out of Level 3				$ 0
Juvenile Diabetes Research Foundation, or JDRF, T1D Fund, or JDRF Note | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Convertible notes						$ 4,000,000
JDRF Note
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Convertible notes						$ 2,000,000
Measurement input period				1 year 7 months 6 days	1 year 10 months 24 days
Recognized gain on fair value adjustments on convertible note				$ 89,000	$ 110,000
Convertible shares | shares			948,225
Conversion price per share | $ / shares			$ 2.294
Percentage of weighted average cost of capital				25.00%
Liquidity event term				9 months 18 days
JDRF Note | Expected Stock Price Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input		0.803		0.803	0.90
JDRF Note | Risk-Free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input		0.003		0.003	0.016
JDRF Note | Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input					0.148
JDRF Note | Dividends
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input		0		0
SAFE
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Proceeds from simple agreement for future equity		$ 6,000,000		$ 6,000,000
Shares converted | shares				333,333

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Prepaid Expense And Other Assets Current [Abstract]
Loss recovery receivable		$ 1,875,000
Contract research	$ 489,000	487,000
Tax receivable	163,000	334,000
Deferred offering costs capitalized	2,256,000	0
Other	469,000	264,000
Total prepaid expenses and other current assets	$ 3,377,000	$ 2,960,000

Prepaid Expenses and Other Cu_4

Prepaid Expenses and Other Current Assets - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Prepaid Expense And Other Assets Current [Abstract]
Loss recovery receivable	$ 1.9

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Employee compensation costs	$ 853	$ 915
Research and development costs	1,083	275
Professional costs	293	243
Other	31	22
Total accrued expenses and other current liabilities	$ 2,260	$ 1,455

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) - USD ($)	1 Months Ended			6 Months Ended
	Jul. 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Obligations under long term debt				$ 1,815,000	$ 3,676,000
Secured Term Loan Facility | Silicon Valley Bank
Debt Instrument [Line Items]
Secured term loan facility amount			$ 10,000,000
Debt instrument initial advance			$ 2,000,000
Debt instrument final maturity date				2024-05
Long term debt payment terms				In response to the financial impact of the COVID-19 coronavirus pandemic, in April 2020 the lender to our Term Loan extended monthly interest-only payments on the Term Loan through November 2021 and the final maturity date on the Term Loan to May 2024.
long term debt frequency of periodic payment				monthly interest-only payments
Obligations under long term debt				$ 0
Secured term loan facility available for borrowing				$ 0
Secured Term Loan Facility | Silicon Valley Bank | Subsequent Event
Debt Instrument [Line Items]
Repayments of principal outstanding	$ 2,000,000
JDRF Note | Series A Prime Redeemable Convertible Preferred Shares
Debt Instrument [Line Items]
Conversion price per share		$ 2.294
Number of outstanding principal and accrued interest converted		948,225

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Provision for contingent losses	$ 0	$ 0

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Shares - Summary of Outstanding Redeemable Convertible Preferred Shares (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Feb. 29, 2020	Jan. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
Class of Stock [Line Items]
Beginning balance					$ 108,020	$ 46,967	$ 43,897
Beginning balance (in shares)					71,324,468	35,524,212	35,524,212
Restructuring								$ 24,977
Restructuring, Shares								19,831,103
Issuance of Series A redeemable convertible preferred shares, net of issuance costs					$ 41,864	$ 17,980		$ 17,966
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)					20,116,868	15,693,109		15,693,109
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note						$ 1,811
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note (in shares)						948,225
Issuance of Series B redeemable convertible preferred shares, net of issuance costs		$ 80,000				$ 39,728
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)	19,158,922	19,158,922				19,158,922
Accretion of redeemable convertible preferred shares to redemption value					$ 2,712	$ 1,534	$ 982	$ 954
Ending balance	$ 152,596	$ 108,020			$ 152,596	$ 108,020	$ 44,879	$ 43,897
Ending balance (in shares)	91,441,336	71,324,468			91,441,336	71,324,468	35,524,212	35,524,212
Series A Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Beginning balance					$ 66,140	$ 46,967	$ 43,897
Beginning balance (in shares)					51,217,321	35,524,212	35,524,212
Restructuring								$ 24,977
Restructuring, Shares								19,831,103
Issuance of Series A redeemable convertible preferred shares, net of issuance costs						$ 17,980		$ 17,966
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)			15,693,109	15,693,109		15,693,109		15,693,109
Accretion of redeemable convertible preferred shares to redemption value					$ 1,465	$ 1,193	$ 982	$ 954
Ending balance	$ 67,605	$ 66,140			$ 67,605	$ 66,140	$ 44,879	$ 43,897
Ending balance (in shares)	51,217,321	51,217,321			51,217,321	51,217,321	35,524,212	35,524,212
Series A Prime Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Beginning balance					$ 1,814
Beginning balance (in shares)					948,225
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note						$ 1,811
Issuance of Series A Prime redeemable convertible preferred shares on conversion of JDRF note (in shares)						948,225
Accretion of redeemable convertible preferred shares to redemption value					$ 45	$ 3
Ending balance	$ 1,859	$ 1,814			$ 1,859	$ 1,814
Ending balance (in shares)	948,225	948,225			948,225	948,225
Series B Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Beginning balance					$ 40,066
Beginning balance (in shares)					19,158,922
Issuance of Series A redeemable convertible preferred shares, net of issuance costs					$ 41,864
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)					20,116,868
Issuance of Series B redeemable convertible preferred shares, net of issuance costs						$ 39,728
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)						19,158,922
Accretion of redeemable convertible preferred shares to redemption value					$ 1,202	$ 338
Ending balance	$ 83,132	$ 40,066			$ 83,132	$ 40,066
Ending balance (in shares)	39,275,790	19,158,922			39,275,790	19,158,922

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Shares - Summary of Outstanding Redeemable Convertible Preferred Shares (Parenthetical) (Details) - USD ($)	1 Months Ended		3 Months Ended			6 Months Ended
	Mar. 31, 2020	Jan. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Series A Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Shares issuance costs net		$ 34,000		$ 20,000	$ 34,000	$ 20,000	$ 33,000
Series B Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Shares issuance costs net	$ 271,000		$ 136,000	$ 271,000		$ 407,000

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Shares - Additional Information (Details) - USD ($)	Jan. 01, 2019	Jul. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Feb. 29, 2020	Jan. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Class of Stock [Line Items]
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)							20,116,868	15,693,109	15,693,109
Issuance of Series B redeemable convertible preferred shares, net of issuance costs				$ 80,000,000				$ 39,728,000
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)			19,158,922	19,158,922				19,158,922
Proceeds from simple agreement for future equity										$ 6,000,000
Shares converted	1
Clinical Development Milestones | Tranche Right
Class of Stock [Line Items]
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)				19,158,922
SAFE
Class of Stock [Line Items]
Proceeds from simple agreement for future equity			$ 6,000,000							$ 6,000,000
Shares converted										333,333
SAFE | Subsequent Event
Class of Stock [Line Items]
Shares converted		333,333
SAFE | Initial Public Offering | Subsequent Event
Class of Stock [Line Items]
Share price, per share		$ 18
JDRF Note
Class of Stock [Line Items]
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)			957,946
Series A Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)					15,693,109	15,693,109		15,693,109	15,693,109
Convertible preferred shares, per share					$ 1.147	$ 1.147
Proceeds from issuance of convertible preferred shares					$ 18,000,000	$ 18,000,000
Shares issuance costs net						$ 34,000		$ 20,000	$ 34,000	$ 20,000	$ 33,000
Series A Prime Redeemable Convertible Preferred Shares | JDRF Note
Class of Stock [Line Items]
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)					948,225
Convertible preferred shares, per share					$ 2.294
Series B Redeemable Convertible Preferred Shares
Class of Stock [Line Items]
Issuance of Series A redeemable convertible preferred shares, net of issuance costs (in shares)							20,116,868
Convertible preferred shares, per share			$ 2.0878	$ 2.0878			$ 2.0878	$ 2.0878		$ 2.0878
Proceeds from issuance of convertible preferred shares			$ 40,000,000	$ 40,000,000
Shares issuance costs net				$ 271,000			$ 136,000	$ 271,000		$ 407,000
Issuance of Series B redeemable convertible preferred shares, net of issuance costs								$ 39,728,000
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)								19,158,922
Series B Redeemable Convertible Preferred Shares | JDRF Note
Class of Stock [Line Items]
Shares issuance costs net			$ 2,000,000

Incentive Shares and Equity-B_3

Incentive Shares and Equity-Based Compensation - Additional Information (Details) - USD ($)	Jan. 01, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average fair value				$ 2.01	$ 1.25
Additional compensation expense		$ 150,000	$ 11,000	$ 210,000	$ 20,000
Incentive shares available for future grant		10,818,083		10,818,083
Incentive shares, grants in period				1,417,844	87,839
Unrecognized compensation cost		$ 3,400,000		$ 3,400,000
Unrecognized compensation cost that is expected to be recognized over a weighted-average period				3 years 4 months 24 days
Incentive Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incentive shares, exchanged in period	209,661
Weighted average fair value	$ 0.66
Stock Options | Incentive Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incentive shares, exchanged in period	195,630
Warrants | Incentive Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incentive shares, exchanged in period	14,031
2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional compensation expense				$ 0
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of incentive shares, authorized		1,717,678		1,717,678		13,182,678

Incentive Shares and Equity-B_4

Incentive Shares and Equity-Based Compensation - Fair Value Assumptions of Incentive Shares Issued Determined Using Black-Scholes Option Pricing Model (Details)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected Term	2 years	1 year 2 months 12 days
Risk Free Rate, Minimum	0.14%	1.96%
Risk Free Rate, Maximum	0.17%	2.60%
Volatility, Minimum	82.70%	71.50%
Volatility, Maximum	83.70%	72.30%
Dividend Yield	0.00%	0.00%

Incentive Shares and Equity-B_5

Incentive Shares and Equity-Based Compensation - Summary of Equity-based Compensation Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	$ 150,000	$ 11,000	$ 210,000	$ 20,000
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	58,000	5,000	70,000	9,000
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	$ 92,000	$ 6,000	$ 140,000	$ 11,000

Astellas Agreement - Additional

Astellas Agreement - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Nov. 30, 2019	Oct. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Short-term deferred revenue			$ 4,748,000		$ 4,748,000		$ 4,365,000
Long-term deferred revenue			4,582,000		4,582,000		$ 6,053,000
License and Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 10,000,000
Revenues			2,000,000	$ 0	4,000,000	$ 0
Contract assets			0		0
Short-term deferred revenue			4,700,000		4,700,000
Long-term deferred revenue			4,600,000		4,600,000
Revenue, remaining performance obligation			25,000,000		$ 25,000,000
License and Collaboration Agreement | Astellas Pharma Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License and collaboration agreement, contractual term		5 years			5 years
Non-refundable upfront payment received	$ 10,000,000
Estimated research funding and external cost reimbursement receivable			17,000,000		$ 17,000,000
Subsequent licensed compounds, milestone payments, right to receive			38,000,000		38,000,000
Transaction price			29,900,000		29,900,000
Estimated research funding and reimbursement of external costs presently budgeted under the agreement			19,900,000		19,900,000
License and Collaboration Agreement | Astellas Pharma Inc. | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
First licensed compound, milestone payments, right to receive			43,000,000		43,000,000
Regulatory milestone payments receivable upon achievement of specified regulatory milestones			105,000,000		105,000,000
Amount eligible to receive from potential commercial milestone payments based on net sales of all licensed products containing same licensed compound, if any licensed products are successfully commercialized			$ 150,000,000		$ 150,000,000

Astellas Agreement - Addition_2

Astellas Agreement - Additional Information (Details1) - License and Collaboration Agreement $ in Millions	Jun. 30, 2020USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 25
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-07-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 7.6
Revenue, remaining performance obligation, expected timing of satisfaction, period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 8.3
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 9.1
Revenue, remaining performance obligation, expected timing of satisfaction, period	1 year

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Provision or benefit for income taxes	$ 0	$ 0

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net loss	$ (9,237)	$ (5,685)	$ (15,657)	$ (11,490)
Change in redemption value of redeemable convertible preferred shares	(2,712)	(982)	(4,245)	(1,936)
Net loss attributable to common shares – basic and diluted	$ (11,949)	$ (6,667)	$ (19,902)	$ (13,426)
Net loss per common share, basic and diluted	$ (10.15)	$ (6.30)	$ (17.23)	$ (13.19)
Weighted-average number of shares outstanding used in computing net loss per common share, basic and diluted	1,177,479	1,057,617	1,154,856	1,018,254

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Redeemable Convertible Preferred Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net loss per share	91,441,336	35,524,212	91,441,336	35,524,212
Incentive Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net loss per share	2,364,595	297,500	2,364,595	297,500
Warrants to Purchase Series A Redeemable Convertible Preferred Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from calculation of diluted net loss per share	55,976		55,976

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended			6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)	19,158,922	19,158,922		19,158,922
Series B Redeemable Convertible Preferred Shares
Related Party Transaction [Line Items]
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)				19,158,922
Convertible preferred shares, per share	$ 2.0878	$ 2.0878	$ 2.0878	$ 2.0878		$ 2.0878
Proceeds from issuance of convertible preferred shares	$ 40,000,000	$ 40,000,000
Executive | General and Administrative
Related Party Transaction [Line Items]
Costs incurred under arrangement			$ 364,000		$ 97,000	$ 599,000	$ 178,000
Executive | Accounts Payable
Related Party Transaction [Line Items]
Amounts owed under arrangement	95,000		95,000			95,000		$ 34,000
Director
Related Party Transaction [Line Items]
Amounts owed under arrangement	$ 0		0			$ 0		$ 0
Related party agreement termination date						2020-07
Director | General and Administrative
Related Party Transaction [Line Items]
Costs incurred under arrangement			$ 25,000		$ 38,000	$ 63,000	$ 75,000
Stockholders and their Affiliates, Executive Officers and Non-employee Directors
Related Party Transaction [Line Items]
Issuance of Series B redeemable convertible preferred shares, net of issuance costs (in shares)	12,883,010	12,883,010
Stockholders and their Affiliates, Executive Officers and Non-employee Directors | Series B Redeemable Convertible Preferred Shares
Related Party Transaction [Line Items]
Percentage of convertible shares sold to related party	5.00%	5.00%

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions	Jul. 13, 2020	Jul. 31, 2020USD ($)shares	Aug. 31, 2020USD ($)shares	Sep. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2020shares	Jul. 21, 2020shares	Jul. 20, 2020shares	Dec. 31, 2019shares
Subsequent Event [Line Items]
Reverse share split					one-for-5.0994
Common shares, outstanding					1,195,794			1,110,767
Common shares, authorized					100,000,000			62,000,000
Forecast
Subsequent Event [Line Items]
Net proceeds after deducting underwriting discounts and commissions but before deducting offering costs | $				$ 142.2
Initial Public Offering | Forecast
Subsequent Event [Line Items]
Number of shares of common stock issued				8,494,166
Convertible preferred shares, per share | $ / shares				$ 18
Subsequent Event
Subsequent Event [Line Items]
Reverse share split, ratio	0.196
Number of shares of common stock issued			994,166
Net proceeds after deducting underwriting discounts and commissions but before deducting offering costs | $			$ 142.2
Common shares, outstanding						28,525,762
Common shares, authorized						200,000,000
Preferred stock, shares authorized						5,000,000
Subsequent Event | Term Loan
Subsequent Event [Line Items]
Repayments of debt | $		$ 2
Subsequent Event | Common Stock | Series A, Series A Prime and Series B Convertible Preferred Stock
Subsequent Event [Line Items]
Convertible preferred stock, shares issued upon conversion							17,950,189
Subsequent Event | Common Stock | Incentive Shares
Subsequent Event [Line Items]
Convertible preferred stock, shares issued upon conversion							1,504,586
2020 Stock Incentive Plan | Subsequent Event
Subsequent Event [Line Items]
Number of shares of common stock reserved for issuance		2,519,375
Annual increase in shares of common stock		6,000,000
Shares issued, percentage of common stock outstanding		4.00%
2020 Stock Incentive Plan | Restricted Common Shares and Incentive Shares | Subsequent Event | Maximum
Subsequent Event [Line Items]
Number of shares of common stock issued		1,504,613
2020 Employee Stock Purchase Plan | Subsequent Event
Subsequent Event [Line Items]
Number of shares of common stock reserved for issuance		209,948
Annual increase in shares of common stock		1,500,000
Shares issued, percentage of common stock outstanding		1.00%