Segment Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2025 USD ($) segment	Mar. 31, 2024 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	1
Number of reportable segments | segment	1
Program specific expenses:
Total research and development expenses	$ 17,760	$ 13,541
General and administrative specific expenses:
Total general and administrative expenses	8,159	5,238
Net loss	(22,647)	(16,921)
Reportable Segment
Program specific expenses:
Total research and development expenses	17,760	13,541
General and administrative specific expenses:
Total general and administrative expenses	8,159	5,238
Other income (expense)	3,272	1,858
Net loss	(22,647)	(16,921)
Rett syndrome | Reportable Segment
Program specific expenses:
Total research and development expenses	4,524	2,019
Batten disease | Reportable Segment
Program specific expenses:
Total research and development expenses	845	1,190
Early Discovery | Reportable Segment
Program specific expenses:
Total research and development expenses	1,287	1,466
Personnel-related | Reportable Segment
Program specific expenses:
Total research and development expenses	5,404	4,718
General and administrative specific expenses:
Total general and administrative expenses	2,484	2,101
Stock-based compensation | Reportable Segment
Program specific expenses:
Total research and development expenses	1,570	564
General and administrative specific expenses:
Total general and administrative expenses	2,478	480
Manufacturing | Reportable Segment
Program specific expenses:
Total research and development expenses	3,107	2,979
Other | Reportable Segment
Program specific expenses:
Total research and development expenses	1,023	605
General and administrative specific expenses:
Total general and administrative expenses	1,288	551
Professional and consultant fees | Reportable Segment
General and administrative specific expenses:
Total general and administrative expenses	1,277	1,502
Office-related | Reportable Segment
General and administrative specific expenses:
Total general and administrative expenses	$ 632	$ 604