Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited interim condensed consolidated financial statements and related disclosures have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).
Principles of Consolidation	Principles of Consolidation The interim condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The U.S. dollar is the functional and reporting currency of the Company and its subsidiaries.
Reverse Stock Split	Reverse Stock Split On September 15, 2020, immediately before the closing of the Merger, resTORbio effected a 1-for-7 reverse stock split of resTORbio’s common stock. Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. No fractional shares were issued in connection with the Reverse Stock Split. Unless otherwise noted, all references to common stock share and per share amounts have also been adjusted to reflect the exchange ratio of 0.1240.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed consolidated balance sheet as of December 31, 2019 was derived from the Company’s audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”), for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission on September 16, 2020. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed consolidated financial position as of September 30, 2020 and condensed consolidated results of operations for the three and nine months ended September 30, 2020 and 2019 and condensed consolidated cash flows for the nine months ended September 30, 2020 and 2019 have been made. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements as well as the reported amounts of revenues and expenses during the reporting period. Such estimates include the valuation of the intangible assets acquired in business combinations, redeemable convertible preferred stock warrant liability, redeemable convertible preferred stock tranche liability, the Technion Research and Development Foundation liability (“TRDF Liability”), contingent consideration liability for contingent value right (“CVR”), deferred tax assets, useful lives of property and equipment, accruals for research and development activities, revenue recognition and stock-based compensation. Actual results could differ from those estimates. The current COVID-19 (coronavirus) pandemic, which is impacting worldwide economic activity, poses risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the coronavirus impacts the Company’s operations will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the duration of the outbreak, new information that will emerge concerning the severity of the coronavirus and the actions to contain the coronavirus or treat its impact, among others. COVID-19 may impact the timing of regulatory approval of the INDs for clinical trials, the enrollment of any clinical trials that are approved, the availability of clinical trial materials and regulatory approval and commercialization of our products. COVID-19 may also impact the Company’s ability to access capital, which could negatively impact short-term and long-term liquidity.
Business Combinations	Business Combinations Business combinations are accounted for under the acquisition method. The Company recognizes the assets acquired and liabilities assumed in business combinations on the basis of their fair values at the date of acquisition. The Company assesses the fair value of assets acquired, including intangible assets, and liabilities assumed using a variety of methods. Each asset acquired and liability assumed is measured at fair value from the perspective of a market participant. The method used to estimate the fair values of intangible assets incorporates significant estimates and assumptions regarding the estimates a market participant would make in order to evaluate an asset, including a market participant’s use of the asset, future cash inflows and outflows, probabilities of success, asset lives, and the appropriate discount rates. Acquired in-process research and development (“IPR&D”) is recognized at fair value and initially characterized as an indefinite-lived intangible asset, irrespective of whether the acquired IPR&D has an alternative future use. Any excess purchase price over the fair value of the net tangible and intangible assets acquired is allocated to goodwill. Transaction costs and restructuring costs associated with a business combination are expensed as incurred. During the measurement period, which extends no later than one year from the acquisition date, the Company may record certain adjustments to the carrying value of the assets acquired and liabilities assumed with the corresponding offset to goodwill. After the measurement period, all adjustments are recorded in the condensed consolidated statements of operations as operating expenses or income.
Contingent Consideration Liability	Contingent Consideration Liability The estimated fair value of contingent consideration liability, initially measured and recorded on the acquisition date, is considered to be a Level 3 instrument. The contingent consideration liability is recorded at fair value at the end of each reporting period with changes in estimated fair values recorded in research and development expenses in the condensed consolidated statements of operations.
Goodwill	Goodwill Goodwill represents the excess of the purchase price over the fair value of net tangible and identified intangible assets acquired in a business combination. Goodwill is not amortized but is evaluated at least annually for impairment or when a change in facts and circumstances indicate that the fair value of the goodwill may be below its carrying value. Goodwill is tested for impairment at the reporting unit level annually in the fourth quarter, or more frequently when events or changes in circumstances indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company has determined that it operates in a single operating segment and has a single reporting unit. Prior to performing the impairment test, the Company assesses qualitative factors to determine whether the existence of events or circumstances would indicate that it is more likely than not that the fair value of the reporting unit was less than its carrying amount. If after assessing the totality of events or circumstances, the Company were to determine that it is more likely than not that the fair value of the reporting unit is less than its carrying amount, then the Company would perform a quantitative impairment test. The quantitative impairment test involves comparing the fair value of the reporting unit to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net assets, goodwill is not impaired, and no further testing is required. If the fair value of the reporting unit is less than the carrying value, the Company measures the amount of impairment loss, if any, as the excess of the carrying value over the fair value of the reporting unit. The Company has determined there were no indicators of goodwill impairment as of September 30, 2020.
Intangible Assets	Intangible Assets In connection with the Merger, the Company acquired certain IPR&D assets, which were classified as indefinite-lived intangible assets. Acquired IPR&D represents the fair value assigned to research and development assets that the Company acquires and have not been completed at the acquisition date. The fair value of IPR&D acquired in a business combination is recorded on the Company’s condensed consolidated balance sheets at the acquisition-date fair value and is determined by estimating the costs to develop the technology into commercially viable products, estimating the resulting revenue from the products, and discounting the projected net cash flows to present value. IPR&D is not amortized, but rather is reviewed for impairment on an annual basis or more frequently if indicators of impairment are present, until the project is completed, abandoned, or transferred to a third party.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB ASC or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued Accounting Standards Update (“ASU”) No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies the disclosure requirements on fair value measurements. The new disclosure requirements include disclosure related to changes in unrealized gains or losses included in other comprehensive income (loss) for recurring Level 3 fair value measurements held at the end of each reporting period and the explicit requirement to disclose the range and weighted-average of significant unobservable inputs used for Level 3 fair value measurements. This ASU removes the requirement to disclose: the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy; the policy for timing of transfers between levels; and the valuation processes for Level 3 fair value measurements. For all entities, this ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. The Company adopted this ASU effective January 1, 2020. The adoption of this ASU did not have a material effect on the Company’s condensed consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). The amendments in ASU 2020-04 provide optional expedients and exceptions for applying generally accepted accounting principles to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in ASU 2020-04 are effective for all entities as of March 12, 2020 through December 31, 2022. An entity may elect to apply the amendments for contract modifications by Topic or Industry Subtopic as of any date from the beginning an interim period that includes or is subsequent to March 12, 2020, or prospectively from the date that the financial statements are available to be issued. Once elected for a Topic or an Industry Subtopic, the amendments must be applied prospectively for all eligible contract modifications for that Topic or Industry Subtopic. The Company may elect to apply ASU 2020-04 as its contracts referenced in London Interbank Offered Rate (“LIBOR”) are impacted by reference rate reform. The Company is currently evaluating the impact of the adoption of this ASU on the Company’s consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2020

The unaudited interim condensed consolidated financial statements and related disclosures have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Principles of Consolidation

The interim condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The U.S. dollar is the functional and reporting currency of the Company and its subsidiaries.

Reverse Stock Split

On September 15, 2020, immediately before the closing of the Merger, resTORbio effected a 1-for-7 reverse stock split of resTORbio’s common stock. Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. No fractional shares were issued in connection with the Reverse Stock Split. Unless otherwise noted, all references to common stock share and per share amounts have also been adjusted to reflect the exchange ratio of 0.1240.

Unaudited Interim Financial Information

The condensed consolidated balance sheet as of December 31, 2019 was derived from the Company’s audited financial statements, but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of September 30, 2020 and for the three and nine months ended September 30, 2020 and 2019, have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”), for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission on September 16, 2020. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s condensed consolidated financial position as of September 30, 2020 and condensed consolidated results of operations for the three and nine months ended September 30, 2020 and 2019 and condensed consolidated cash flows for the nine months ended September 30, 2020 and 2019 have been made. The results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.

Use of Estimates

The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements as well as the reported amounts of revenues and expenses during the reporting period. Such estimates include the valuation of the intangible assets acquired in business combinations, redeemable convertible preferred stock warrant liability, redeemable convertible preferred stock tranche liability, the Technion Research and Development Foundation liability (“TRDF Liability”), contingent consideration liability for contingent value right (“CVR”), deferred tax assets, useful lives of property and equipment, accruals for research and development activities, revenue recognition and stock-based compensation. Actual results could differ from those estimates. The current COVID-19 (coronavirus) pandemic, which is impacting worldwide economic activity, poses risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period of time, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the coronavirus impacts the Company’s operations will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the duration of the outbreak, new information that will emerge concerning the severity of the coronavirus and the actions to contain the coronavirus or treat its impact, among others. COVID-19 may impact the timing of regulatory approval of the INDs for clinical trials, the enrollment of any clinical trials that are approved, the availability of clinical trial materials and regulatory approval and commercialization of our products. COVID-19 may also impact the Company’s ability to access capital, which could negatively impact short-term and long-term liquidity.

Business Combinations

Business combinations are accounted for under the acquisition method. The Company recognizes the assets acquired and liabilities assumed in business combinations on the basis of their fair values at the date of acquisition. The Company assesses the fair value of assets acquired, including intangible assets, and liabilities assumed using a variety of methods. Each asset acquired and liability assumed is measured at fair value from the perspective of a market participant. The method used to estimate the fair values of intangible assets incorporates significant estimates and assumptions regarding the estimates a market participant would make in order to evaluate an asset, including a market participant’s use of the asset, future cash inflows and outflows, probabilities of success, asset lives, and the appropriate discount rates. Acquired in-process research and development (“IPR&D”) is recognized at fair value and initially characterized as an indefinite-lived intangible asset, irrespective of whether the acquired IPR&D has an alternative future use. Any excess purchase price over the fair value of the net tangible and intangible assets acquired is allocated to goodwill. Transaction costs and restructuring costs associated with a business combination are expensed as incurred.

During the measurement period, which extends no later than one year from the acquisition date, the Company may record certain adjustments to the carrying value of the assets acquired and liabilities assumed with the corresponding offset to goodwill. After the measurement period, all adjustments are recorded in the condensed consolidated statements of operations as operating expenses or income.

Contingent Consideration Liability

The estimated fair value of contingent consideration liability, initially measured and recorded on the acquisition date, is considered to be a Level 3 instrument. The contingent consideration liability is recorded at fair value at the end of each reporting period with changes in estimated fair values recorded in research and development expenses in the condensed consolidated statements of operations.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of net tangible and identified intangible assets acquired in a business combination. Goodwill is not amortized but is evaluated at least annually for impairment or when a change in facts and circumstances indicate that the fair value of the goodwill may be below its carrying value.

Goodwill is tested for impairment at the reporting unit level annually in the fourth quarter, or more frequently when events or changes in circumstances indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company has determined that it operates in a single operating segment and has a single reporting unit.

Prior to performing the impairment test, the Company assesses qualitative factors to determine whether the existence of events or circumstances would indicate that it is more likely than not that the fair value of the reporting unit was less than its carrying amount. If after assessing the totality of events or circumstances, the Company were to determine that it is more likely than not that the fair value of the reporting unit is less than its carrying amount, then the Company would perform a quantitative impairment test.

The quantitative impairment test involves comparing the fair value of the reporting unit to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net assets, goodwill is not impaired, and no further testing is required. If the fair value of the reporting unit is less than the carrying value, the Company measures the amount of impairment loss, if any, as the excess of the carrying value over the fair value of the reporting unit. The Company has determined there were no indicators of goodwill impairment as of September 30, 2020.

Intangible Assets

In connection with the Merger, the Company acquired certain IPR&D assets, which were classified as indefinite-lived intangible assets. Acquired IPR&D represents the fair value assigned to research and development assets that the Company acquires and have not been completed at the acquisition date. The fair value of IPR&D acquired in a business combination is recorded on the Company’s condensed consolidated balance sheets at the acquisition-date fair value and is determined by estimating the costs to develop the technology into commercially viable products, estimating the resulting revenue from the products, and discounting the projected net cash flows to present value. IPR&D is not amortized, but rather is reviewed for impairment on an annual basis or more frequently if indicators of impairment are present, until the project is completed, abandoned, or transferred to a third party.

Recent Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB ASC or other standard setting bodies and adopted by the Company as of the specified effective date, unless otherwise discussed below.

Recently Adopted Accounting Pronouncements

In August 2018, the FASB issued Accounting Standards Update (“ASU”) No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies the disclosure requirements on fair value measurements. The new disclosure requirements include disclosure related to changes in unrealized gains or losses included in other comprehensive income (loss) for recurring Level 3 fair value measurements held at the end of each reporting period and the explicit requirement to disclose the range and weighted-average of significant unobservable inputs used for Level 3 fair value measurements. This ASU removes the requirement to disclose: the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy; the policy for timing of transfers between levels; and the valuation processes for Level 3 fair value measurements. For all entities, this ASU is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. The Company adopted this ASU effective January 1, 2020. The adoption of this ASU did not have a material effect on the Company’s condensed consolidated financial statements and related disclosures.

Recently Issued Accounting Pronouncements

In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). The amendments in ASU 2020-04 provide optional expedients and exceptions for applying generally accepted accounting principles to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The amendments in ASU 2020-04 are effective for all entities as of March 12, 2020 through December 31, 2022. An entity may elect to apply the amendments for contract modifications by Topic or Industry Subtopic as of any date from the beginning an interim period that includes or is subsequent to March 12, 2020, or prospectively from the date that the financial statements are available to be issued. Once elected for a Topic or an Industry Subtopic, the amendments must be applied prospectively for all eligible contract modifications for that Topic or Industry Subtopic. The Company may elect to apply ASU 2020-04 as its contracts referenced in London Interbank Offered Rate (“LIBOR”) are impacted by reference rate reform. The Company is currently evaluating the impact of the adoption of this ASU on the Company’s consolidated financial statements.