California layoffs / Arsenal Biosciences, Inc.

Arsenal Biosciences, Inc. California Layoffs 2025: What Employees Should Know

Arsenal Biosciences, Inc. has a layoff notice on file with California's Employment Development Department (EDD) under the state's Worker Adjustment and Retraining Notification (WARN) Act, covering 100 jobs in San Mateo County. That is what the state has published since July 2025. If you were one of them, here is what the filing says, how much notice the law asks for, and what to look at before you sign anything.

What the filing says

These are the details as Arsenal Biosciences, Inc. reported them to the state. The EDD publishes every notice, and this page reflects the data as of Jul 31, 2026.

Location	County	Notice given	Jobs end	Workers	Type
South San Francisco	San Mateo County	Sep 16, 2025	Nov 14, 2025	100	Layoff Permanent

How much notice the law requires

California's WARN Act requires 60 days of advance written notice before a covered mass layoff. What makes the California version unusual is how few ways out it gives an employer. The only statutory exception is a physical calamity or an act of war. Federal law has three exceptions, including one for unforeseeable business circumstances, and the California Legislature deliberately declined to copy them.

What this filing shows

This filing shows 59 calendar days between the notice date and the date the jobs end. That is less than the 60 days the statute describes.

This is a fact drawn from the public filing, not a conclusion that anyone broke the law. The date an employer records is not always the date workers were told, employers of different sizes are covered differently, and exceptions can apply. Whether it means anything in your case is exactly what a free consultation sorts out.

Arsenal Biosciences severance: what to check before you sign

A severance offer is not the same thing as the notice pay the WARN Act describes, and an employer cannot use one to satisfy the other. A release may also give up more than you expect, and an arbitration agreement you signed at hire can affect where a dispute is heard. Read our full guide to the California WARN Act before you decide, and consider having the paperwork looked at.

Two things worth doing this week either way. File for unemployment now, because WARN money does not reduce it. And keep every document, including the notice itself and anything showing when it arrived.

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Questions people are asking

What is the Arsenal Biosciences severance package?

The WARN notice Arsenal Biosciences filed with the state does not list severance terms, and we do not publish any employer's package. A WARN notice reports how many jobs end, where, and when. Severance is a separate contract offered at the employer's discretion. California law does not require it, and an employer cannot use contractual severance to satisfy what the WARN Act requires, so being offered a package does not by itself answer whether notice pay is also owed. If you have an offer in hand, the terms in front of you are the ones that matter, and they are worth reading closely before the deadline on them runs.

Am I owed severance from Arsenal Biosciences, Inc.?

California law does not require severance on its own, and a severance offer is a separate thing from WARN pay. An employer cannot use contractual severance to satisfy its WARN obligation, so being offered a package does not answer whether notice pay is also owed.

Does taking the severance reduce what I could recover?

It depends on why the money is being paid. Severance the employer was already obligated to provide — under a contract, a policy, a benefit plan, or a union agreement — cannot be set against what the WARN Act requires. A payment that is genuinely voluntary and unconditional, one the employer had no legal obligation to make, can reduce that liability. Wages for work you actually performed during the notice period are not voluntary severance at all. Which category an offer falls into is a question about the document in front of you, not about the layoff, and it is one of the better reasons to have the paperwork read before the deadline on it runs.

What if I did not get 60 days of notice?

California's WARN Act requires 60 days of advance written notice before a covered mass layoff, and its only statutory exception is a physical calamity or an act of war. That is far narrower than federal law, which has three exceptions. The shortest gap in this filing is 59 days, which is 1 short of 60. That is arithmetic on two published dates and not a finding that anyone broke the law: the recorded date is not always the date workers were told, and coverage depends on the employer's size and how many people were let go.

Can I still collect unemployment?

Yes. Under Labor Code section 1407, WARN-related payments are not treated as wages for unemployment purposes, so they cannot be used to deny or reduce your benefits in California. You do not have to wait for your last day — the filings here run through Nov 14, 2025 — and filing early is generally better than filing late.

Does taking a new job hurt my claim?

No. Wages you earn at a new job during the notice period do not reduce what a former employer may owe under WARN. You do not need to delay a job search to protect a claim.

How long do I have to act?

Generally three years. The federal WARN Act sets no limitations period of its own, so courts borrow the closest state deadline, which in California is the three-year period for a liability created by statute. The clock starts when you suffer an employment loss, not when the notice went out. Measured from the last day of work in this filing, Nov 14, 2025, three years runs to about Nov 14, 2028. If this was a layoff rather than an outright termination, the loss may not count until the layoff has lasted more than six months, which can start the clock later still. Treat all of it as an outer edge rather than a plan. Other claims arising from the same layoff run much shorter, and a severance offer usually carries its own deadline measured in days.

What has been reported

Press coverage of this layoff, summarized and attributed. This is reporting rather than the filing itself, and we did not independently verify it.

The 100-worker layoff at ArsenalBio's South San Francisco headquarters, effective November 14, 2025, cut roughly 50% of the CAR T-cell therapy developer's staff as it restructured from early-stage research into a clinical-stage company, Fierce Biotech reported; the company said it now employs 127 people.

A company spokesperson said the reorganization was undertaken to "extend our cash runway and position the organization for our next phase of development," with efforts concentrated on lead asset AB-2100, an autologous cell therapy in a phase 1/2 trial for recurrent clear-cell renal cell carcinoma, per Fierce Biotech.

KRON4 reported the cuts came about a year after Arsenal Biosciences raised a $325 million Series C round, and that state filings indicate all of the layoffs at the Oyster Point Boulevard headquarters are permanent.

Details worth knowing

The restructuring does not affect ArsenalBio's longstanding collaboration with Bristol Myers Squibb on CAR-T cell therapies for solid tumors, which continues, according to Fierce Biotech.

Sources: Fierce Biotech (opens in a new tab)KRON4 (opens in a new tab)

What the numbers show

The 100 affected positions are in South San Francisco.
By headcount it sits in the top 40% of the 593 employer layoffs tracked here.
The 100 workers leaving Arsenal Biosciences, Inc. re-enter a job market where San Mateo County unemployment stood at 3.6% in June 2026, below the 5.2% statewide rate (Bureau of Labor Statistics, not seasonally adjusted).

These are counts and comparisons drawn from the published filings, not findings about Arsenal Biosciences.

Free job-search help near South San Francisco

America's Job Center of California is the state's no-cost network for laid-off workers: help filing and keeping unemployment benefits, federally funded retraining, and résumé and interview coaching. Your WARN notice may name one; this is the closest to the site in this filing.

Human Services Agency of San Francisco (opens in a new tab)
3120 Mission Street, San Francisco, CA 94110 · 415-401-4800
Affiliate center (partial services) · about 6.1 miles from the South San Francisco site

Locations and hours change — confirm before visiting, or find another center with the EDD's center locator (opens in a new tab). Directory: U.S. Department of Labor, Jul 31, 2026; distances are straight-line from the address in the filing.

Other layoffs filed in San Mateo County around the same time

33 employers have WARN notices on file in San Mateo County, covering 6,053 workers. These filed within about a quarter of this one.

Listed because they appear in the same county in the same public data. No connection between these employers is implied.

Key points

Each point is explained and sourced above · Verified July 31, 2026

Workers affected · San Mateo County · published since July 2025
100
CA EDD WARN report
Notices filed · California · published July 2025 to July 2026
1
CA EDD WARN report
Jobs end · As filed
Nov 14, 2025
CA EDD WARN report
Days between notice and last day · Arithmetic on two published dates
59 calendar days
CA EDD WARN report
San Mateo County unemployment rate · vs 5.2% statewide, not seasonally adjusted
3.6% (June 2026)
BLS Local Area Unemployment Statistics
Notice California law describes · California
60 days before a covered mass layoff
Lab. Code § 1401
Available exceptions · California
Physical calamity or act of war only
Lab. Code § 1401

Cite this page

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About this data

Where it comes from. Every figure on this page is reproduced from the WARN report the California Employment Development Department publishes at edd.ca.gov (opens in a new tab), retrieved Jul 31, 2026. Employers file these notices with the state, and the state publishes them as a public record.

We make no representation that it is accurate or complete. We reproduce the state's file as published and do not independently verify it. Notices are amended and withdrawn, employers correct their own filings, layoffs are called off, and the published report can lag or contain errors. Nothing here is a substitute for the EDD's own record, and if the two disagree, the EDD's is the one that counts.

How employers are grouped. The EDD's report lists one row per notice and often names the same employer several ways — with a store or site number, a warehouse code, a per-location name, or a spelling variation. This tracker groups those filings under one employer so a company's notices appear on a single page; every underlying filing still appears as its own row in that page's table. The grouping is ours, not the EDD's, and it never combines differently named companies, even ones related through ownership.

Nothing here says an employer did anything wrong. Filing a WARN notice is what the law asks an employer to do, so appearing in this data reflects compliance with the notice requirement rather than a violation of it. Where we show the number of days between a notice and the last day of work, that is arithmetic on two published dates and not a legal conclusion. The date recorded in a filing is not necessarily the date employees were told, employers of different sizes carry different obligations, and statutory exceptions can apply. Whether any particular layoff complied with the law is a fact-specific question that this page does not answer.

This page is general information about California law, not legal advice, and reading it does not create an attorney-client relationship. It is not affiliated with, endorsed by, or sponsored by Arsenal Biosciences, Inc., and any company names are used only to identify publicly filed notices.

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