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

Quarterly report pursuant to Section 13 or 15(d)

Cover
- Document and Entity Information
Financial Statements
Notes to Financial Statements
Accounting Policies
- Summary of Significant Accounting Policies (Policies)
Notes Tables
Notes Details

Loan and Security Agreement - Additional Information (Details)

v3.19.1

Loan and Security Agreement - Additional Information (Details)	1 Months Ended	3 Months Ended
	Aug. 31, 2017 USD ($) Installment	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Oct. 01, 2018 shares	Jul. 31, 2018 USD ($)
Debt Instrument [Line Items]
Debt, non-current		$ 8,500,000		$ 10,000,000
Interest expense, debt		400,000	$ 400,000
Two Thousand Seventeen Warrants
Debt Instrument [Line Items]
Estimated fair value portion of preferred stock						$ 300,000
Two Thousand Seventeen Warrants \| Series E Redeemable Convertible Preferred Stock
Debt Instrument [Line Items]
Warrant to purchase stock \| shares					46,359
August 2017 Loan
Debt Instrument [Line Items]
Debt, current		5,800,000
Debt, non-current		8,500,000
Interest payable	$ 600,000	$ 300,000
Average interest rate		8.90%
Final payment fee percentage	3.83%
Loan and accretion of debt discount		$ 42,000	$ 38,000
August 2017 Loan \| Floating Rate
Debt Instrument [Line Items]
Interest charges on loan	7.39%
August 2017 Loan \| LIBOR
Debt Instrument [Line Items]
Interest charges on loan	6.40%
Description of interest charges on loan		the sum of the 30-day U.S. Dollar London Interbank Offered Rate (“LIBOR”) plus 6.40%.
Loan and Security Agreement \| Oxford Finance LLC and Silicon Valley Bank \| August 2017 Loan
Debt Instrument [Line Items]
Borrowed amount	$ 15,000,000
Loan and Security Agreement \| Oxford Finance LLC and Silicon Valley Bank \| August 2017 Loan \| March 2019
Debt Instrument [Line Items]
Number of monthly installments \| Installment	30
Payment terms, description		The loan is due in 30 monthly installments from March 2019 through its repayment in August 2021, with interest-only monthly payments until March 2019.
Repayment installment, start date, month and year	2019-03
Repayment installment, end date, month and year	2021-08
Frequency of interest-only payments		monthly payments
Interest-only payments, maturity month and year	2019-03

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