Sutro Biopharma, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Collaboration Agreements and Supply Agreements - Additional Information (Details)

Collaboration Agreements and Supply Agreements - Additional Information (Details)		1 Months Ended								3 Months Ended		9 Months Ended
	Oct. 01, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Aug. 31, 2018 USD ($) Program	Jul. 31, 2018 Program	Aug. 31, 2017 USD ($) Program	Jun. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2018 USD ($)	Jul. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable, related parties		$ 1,695,000								$ 1,695,000		$ 1,695,000		$ 784,000
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs												84,739,000	$ 0
Accounts receivable		2,443,000								2,443,000		2,443,000		1,624,000
Series E Redeemable Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs											$ 85,400,000
Subsequent Event \| Common Stock \| IPO
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock, shares \| shares	5,667,000
Share issue price per share \| $ / shares	$ 15.00
SutroVax
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable		584,000								584,000		584,000		34,000
2014 Celgene Agreement \| Celgene
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front, nonrefundable payment received								$ 83,100,000
Revenue recognized from payments ratably over period								3 years
Contingent payment received							$ 15,000,000
Milestone payment received						$ 25,000,000
Deferred revenue					$ 8,200,000
2017 Celgene Agreement \| Celgene
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from payments ratably over period					3 years
Number of programs advancing through preclinical development \| Program					4
Option fee payment received					$ 12,500,000
Second option fee payment received					$ 12,500,000
Number of investigational new drug program \| Program					1
Recognized of deferred revenue over the entire period					$ 12,500,000
Milestone revenue recognized		10,000,000
Deferred revenue		13,100,000								13,100,000		13,100,000		18,000,000
Potential milestone future payment received of manufacturing activities		10,000,000								10,000,000		10,000,000
Accounts receivable, related parties		$ 300,000								300,000		300,000		800,000
2017 Celgene Agreement \| Celgene \| Licensed Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum aggregate milestone and option fee payments eligible to receive												295,000,000
2017 Celgene Agreement \| Celgene \| Other Licensed Products
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum aggregate milestone and option fee payments eligible to receive												393,700,000
2018 Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue from other related parties										$ 300,000		$ 3,900,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from payments ratably over period		4 years								4 years		4 years
Deferred revenue		$ 57,200,000								$ 57,200,000		$ 57,200,000
Number of research programs \| Program				3
Upfront payment received			$ 60,000,000
Number of target programs \| Program			2
Starting term of recognizing revenues from up front payment												2018-07
Revenue recognition aggregate milestone payments eligible to receive												$ 1,600,000,000
Revenue recognition milestone method description												If one or more products from each of the target programs are developed for non-oncology or a single indication, the Company will be eligible for reduced aggregate milestone payments. In addition, the Company is eligible to receive tiered royalties ranging from mid-single digit to low teen percentages on the worldwide sales of any commercial products that may result from the collaboration.
Accounts receivable		$ 800,000								$ 800,000		$ 800,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Subsequent Event \| Common Stock \| IPO
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock, shares \| shares	666,666
Share issue price per share \| $ / shares	$ 15.00
Proceeds from issuance of common stock	$ 10,000,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Subsequent Event \| Series E Redeemable Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock, shares \| shares	74,794,315
Share issue price per share \| $ / shares	$ 0.2674
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	$ 20,000,000
Collaboration Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front, nonrefundable and non-creditable payment received									$ 10,000,000
MDA Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from payments ratably over period		5 years								5 years		5 years
Deferred revenue		$ 2,800,000								$ 2,800,000		$ 2,800,000		5,900,000
Starting term of recognizing revenues from up front payment												2014-06
Up-front, nonrefundable and non-creditable payment received								$ 10,000,000
Maximum amount eligible to receive for each product developed												$ 52,500,000
Accounts receivable		700,000								700,000		700,000		$ 800,000
Supply Agreement \| SutroVax
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable, related parties		$ 600,000								600,000		600,000
Other revenue-related parties										$ 600,000		$ 1,500,000
Research Development and Commercialization Agreement \| The Leukemia & Lymphoma Society, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum contribution in clinical development					6,000,000
Initial milestone payment					500,000
Total milestone payments received					$ 1,000,000
Research development and commercialization agreement termination period					12 years
Research development and commercialization agreement termination description					The LLS Agreement terminates upon the earlier of (a) fulfillment of all payment obligations by both parties or (b) 12 years after the effective date. LLS may terminate the LLS Agreement at any time with 60 days’ prior written notice. Either the Company or LLS has the right to terminate the LLS Agreement based on the other party’s uncured material breach.
Other liabilities related to payments received					$ 1,000,000