Gilead doubles down on Arcus

Despite TIGIT setbacks Gilead has kept faith with Arcus’s domvanalimab, and last night the big biotech doubled down with a new $320m equity investment. The move increases Gilead’s stake in Arcus to 33%, and gives the smaller partner cash until 2027.

There was also a shuffling of domvanalimab’s clinical trial deck: gone is the Arc-10 study of domvanalimab plus the PD-1 inhibitor zimberelimab in high PD-L1-expressing NSCLC, a setting in which the doublet underwhelmed in earlier trials. The companies are now focused on Star-121, a study testing a chemo-containing triplet in all-comers, though it should be noted that this, like Arc-10, includes Keytruda as active control.

Meanwhile, a mysterious new NSCLC study, Star-131, could be in the adjuvant and/or neoadjuvant setting, Mizuho analysts speculated – an area in which PD-(L)1 inhibitors are already making inroads.

Outside NSCLC, the partners highlighted gastric cancers, where the Star-221 trial is ongoing. However, data from the earlier Gastric-Edge study, presented last year, were far from emphatic, particularly in all comers.

In gastric cancer Truist analysts see potential peak sales of $1.8bn, and cited limited competition. That said, other TIGIT hopefuls are advancing in oesophageal and gastroesophageal junction cancers, tumour types included in Star-221.

Enthusiasm

A relevant question, given Gilead's continued interest in Arcus, is what the senior partner might have seen to spur such enthusiasm. Truist claimed that the companies had "not seen any phase 3 data that may have led to the reprioritisation".

While Gilead is still keen on domvanalimab, it seems to be cooling on another Arcus project, the CD37 inhibitor quemliclustat. The big group opted into this asset in 2021, but yesterday said that a phase 3 trial in pancreatic cancer would now be Arcus’s sole responsibility. Still, Mizuho noted that Gilead hadn't formally opted out.

The analysts welcomed the partners’ move towards more “commercially relevant” populations for domvanalimab, and investors were also apparently happy, sending Arcus’s shares up 15% in the premarket today. Perhaps some might be hoping that the latest deal is just a stepping stone to a full buyout.

What’s in, what’s out: Gilead and Arcus’s collaboration

Source: OncologyPipeline & company releases.