ANAB Stock Falls After It Sues GSK Unit Tesaro Again, Claims Fresh Breach Of 2014 Deal

• Anaptys alleges that Tesaro violated the terms of the 2014 deal between the two companies. 
• The company said that it approached Tesaro to resolve the claims, but Tesaro initiated a lawsuit against it.
• A trial is now anticipated in July 2026, and milestone and royalty payments continue to be due to Anaptys during the proceedings.

AnaptysBio, Inc. (ANAB) said on Friday that it has initiated litigation against GSK unit Tesaro, alleging a breach of the terms of the collaboration agreement between the two companies, inked in March 2014. This renewed battle adds to a fraught relationship between the two companies, with a trial now expected in July next year.

ANAB shares dipped 10% in the pre-market session at the time of writing.

New Legal Fight

Anaptys has requested that the court declare that Anaptys is entitled to all rights and remedies under the collaboration agreement. The company alleged that Tesaro violated exclusivity obligations by participating in past, ongoing, and upcoming governed clinical trials with PD-1 antagonists, a type of immunotherapy, and failed to use commercially reasonable efforts to obtain optimum commercial return for its immunotherapy called Jemperli. A trial is now anticipated in July 2026 and milestone and royalty payments continue to be due to Anaptys during the proceedings.

The company said that it approached Tesaro to resolve the claims, but Tesaro initiated a lawsuit against it. Tesaro, in turn, alleges that Anaptys breached the agreement between the two companies. Anaptys said that Tesaro’s claims are entirely without merit and that it intends to pursue all appropriate legal remedies against Tesaro.

Previous Litigation

Anaptys filed a complaint previously against GSK in 2020, alleging that GSK’s planned trial of Zejula in combination with Merck’s Keytruda violated the exclusivity obligations under the 2014 deal.

The complaint resulted in a settlement that included a cash payment.

$100M Stock Repurchase Plan

Separately, Anaptys also announced that its Board of Directors has authorized an amended stock repurchase plan under which the company may repurchase up to $100 million of the company’s outstanding common stock. This is in addition to the $6.4 million that remained as of Nov. 20, 2025, under the current $75 million stock repurchase plan.

The shares may be repurchased from time to time in open market transactions, and the stock repurchase plan will expire on March 31, 2026, the company said.

How Did Stocktwits Users React?

On Stocktwits, retail sentiment around ANAB stayed within the ‘neutral’ territory over the past 24 hours while message volume stayed at ‘extremely low’ levels.

ANAB stock has nearly tripled this year and gained 78% over the past 12 months. 

Also See: Foxconn To Pour Up To $5B Into US Plants After Striking Servers Deal With OpenAI

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