Alphyn Capital targets AnaptysBio royalty upside in GSK dispute

Alphyn Capital Management identified AnaptysBio as a new position initiated late in the second quarter, according to its Q2 2026 investor letter. The investment manager’s thesis focused on royalties linked to GSK’s Jemperli cancer treatment and a dispute over GSK’s commercialisation obligations.

The letter described AnaptysBio as a streamlined royalty business after an April separation moved its clinical pipeline into a new company. Alphyn said the remaining business had fewer than 10 employees and expected annual expenses below US$10 million.

Alphyn said AnaptysBio’s Jemperli royalty starts at 8% and rises to 25% on annual sales above US$2.5 billion. Jemperli generated more than US$1.1 billion in sales in 2025, while GSK reportedly targeted sales above US$2.7 billion.

According to Alphyn, AnaptysBio argued that GSK was required to pursue the “optimal commercial return” for Jemperli but had instead favoured combinations involving Merck’s competing Keytruda. The letter said a related dispute had previously resulted in an improved royalty rate for AnaptysBio, while a Delaware court in April dismissed a GSK counterclaim that could have reduced the rate by half.

Alphyn estimated a base value of about US$55 to US$65 a share, based on contracted royalties, net cash and an authorised buyback programme. It put a potential value of roughly US$70 to US$105 a share on a settlement or ruling that strengthened GSK’s obligations or improved AnaptysBio’s royalty economics. The letter said a trial was scheduled to begin on 14 July 2026; its outcome and current status were not provided in the supplied material. AnaptysBio closed at US$56.60 on 8 September.