Cabaletta Bio, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Common Stock - Additional Information (Details)

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended	9 Months Ended
	Oct. 23, 2019	May 31, 2023	Dec. 31, 2022	Oct. 31, 2019	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Oct. 31, 2023	Jun. 01, 2023	Jan. 01, 2023	Jan. 01, 2022	Oct. 30, 2019	Jan. 31, 2019
Class Of Stock [Line Items]
Common stock, authorized shares			150,000,000			150,000,000
Non-voting common stock, Terms of conversion				Each share of the Company’s non-voting common stock may be converted at any time into one share of common stock at the option of its holder by providing 61 days written notice to the Company
Common stock issuance					$ 93,755
Pre-Funded Warrants Exercised						3,868,184
Addition in pre funded warrants exercised								1,177,538
shares remaining available for issuance						2,926,285
Warrants exercised						3,868,184
Weighted average grant-date fair value of stock options granted						$ 9.27	$ 2.1
Unrecognized compensation cost related to unvested stock-based awards						$ 26,578
Unrecognized compensation cost, period for recognition						2 years 9 months 18 days
At-The-Market Offering Sales Agreement
Class Of Stock [Line Items]
Common stock issuance, Shares						0
Termination, shares						4,792,562
Common stock, par value						$ 0.00001
At-The-Market Offering Sales Agreement \| Maximum
Class Of Stock [Line Items]
Common stock issuance						$ 100,000
December 2022 Financing
Class Of Stock [Line Items]
Common stock issuance, Shares			126,815
Common stock price per share			$ 5.52
May 2023 Financing
Class Of Stock [Line Items]
Common stock issuance, Shares		8,337,500
May 2023 Financing \| Employee Stock Option
Class Of Stock [Line Items]
Additional Options to be purchased by underwriters		1,087,500
2018 Plan \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation unvested number of shares						0
Number of options granted						1,959,411
2018 Plan \| Maximum \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation, vesting period						4 years
2018 Plan \| Minimum \| Employee Stock Option
Class Of Stock [Line Items]
Share-based compensation, vesting period						3 years
2019 Plan
Class Of Stock [Line Items]
Shares reserved for issuance	2,342,288									1,177,805
Increase in share reserved percentage	4.00%
2019 Plan \| Employee Stock Option
Class Of Stock [Line Items]
Number of options granted						2,516,650
2019 ESPP
Class Of Stock [Line Items]
Shares reserved for issuance	234,229									0	0
2019 ESPP \| Minimum
Class Of Stock [Line Items]
Shares reserved for issuance													234,229
Increase in share reserved percentage	1.00%
Payroll deduction percentage of eligible compensation						15.00%
Employee stock purchase plan maximum annual rights to purchase common stock						$ 25
Percentage of shares to be purchased						85.00%
Voting Common Stock
Class Of Stock [Line Items]
Common stock, authorized shares			143,590,481			143,590,481						143,590,481
Common stock, par value			$ 0.00001			$ 0.00001
Voting Common Stock \| 2019 Plan
Class Of Stock [Line Items]
Shares reserved for issuance									3,000,000
Non-voting Common Stock
Class Of Stock [Line Items]
Common stock, authorized shares			6,409,519			6,409,519						6,409,519
Common stock, par value			$ 0.00001			$ 0.00001
Pre-funded Warrants \| December 2022 Financing
Class Of Stock [Line Items]
Common stock issuance, Shares			6,213,776
Common stock price per share			$ 5.51999
Decrease in exercise price of Warrents		$ 12	$ 0.00001
Pre-Funded Warrants Exercised		6,295
Net proceeds from exercise of warrants		$ 93,755	$ 32,562
Warrants exercised		6,295