Arsenal Biosciences, Inc. layoff notices at a glance
Arsenal Biosciences, Inc. has filed 2 WARN notices with the California Employment Development Department between Sep 16, 2025 and Aug 30, 2026, naming 158 workers. All were layoffs rather than closures; 2 permanent, 0 temporary. The largest single notice named 100 workers in San Mateo County on Sep 16, 2025. Its latest notice, 58 workers in San Mateo County dated Aug 30, 2026, was 4.4% of the 1,309 workers named in all 9 San Mateo County notices of fiscal year 2026-2027. 2 of the notices show fewer than 60 days between the notice date and the effective date (see how to read this).
Industry as reported to the EDD: Professional Scientific and Technical Services.
Every notice, newest first
| Notice date | Effective | County | City | Workers | Type | Days notice |
|---|---|---|---|---|---|---|
| Aug 30, 2026 | Oct 28, 2026 | San Mateo | South San Francisco | 58 | Layoff, permanent | 59 under 60 |
| Sep 16, 2025 | Nov 14, 2025 | San Mateo | South San Francisco | 100 | Layoff, permanent | 59 under 60 |
Sites named on the notices
- 329 Oyster Point Blvd South San Francisco CA 94080 (Aug 30, 2026, 58 workers)
- 329 Oyster Point Blvd. South San Francisco CA 94080 (Sep 16, 2025, 100 workers)
Where the notices landed
- San Mateo County2 notices, 158 workers
- South San Francisco2 notices, 158 workers
Local pages: San Mateo County employment law guide.
How to read this record
Notice date is the date on the employer's letter. Effective is the first day of separations it announced. Days notice is the gap between them; California Labor Code 1401 calls for 60 days from a covered employer, and section 1402 makes a short notice worth a day of pay and benefits for every day it is short, up to 60.
For Arsenal Biosciences, Inc. the shortest gap shown is 59 days. That is a reason to check whether an exception in 1401(c) or 1402.5 applied, whether the workers received the letter earlier than the EDD did, and whether anyone was let go before the effective date. It is not, by itself, a finding against the employer.
Full statute walk-through: the California 60-day rule, section by section.
If you work, or worked, at Arsenal Biosciences, Inc.
Keep the notice, every email about the selection, and your final pay stub. A free review covers four things in one call: whether the notice period was honored and paid, whether final pay and vacation payout arrived on time, whether the selection pattern raises an age, pregnancy or leave, or retaliation question, and what a proposed severance release is actually worth before you sign it. Call (800) 371-3088 or send the notice.
Source: California EDD WARN reports, fiscal years 2025-2026 to 2026-2027. Record last checked against the EDD on Oct 30, 2026. Back to the layoff tracker.
About this data: Notices come from the California Employment Development Department WARN reports (fiscal years 2014-2015 to today) and are reloaded from the EDD every Tuesday and Thursday. Employer names appear as the employer wrote them on the notice, grouped where the names clearly refer to the same company. A notice is not a finding that any law was broken. This page is general information, not legal advice about your situation.