Gilead deepens investment in Arcus and TIGIT drugs

Dive Brief:

• Gilead has bought a bigger stake in cancer drug developer Arcus Biosciences, announcing Monday it will spend $320 million to own 33% of the company and help speed development of an experimental immunotherapy.
• With the transaction, the two companies committed to accelerating two trials of Arcus’ drug domvanalimab, which targets a protein called TIGIT, alongside a so-called PD-1 inhibitor and chemotherapy in lung and gastrointestinal cancer. Simultaneously, they are terminating an existing trial of domvanalimab and the PD-1 drug, zimberelimab, in lung cancer.
• Gilead and Arcus said the investment “reflects the companies’ continued conviction in the TIGIT pathway,” an area of research that so far has not lived up to expectations. TIGIT-targeting drugs developed by Merck & Co. and Roche fell short in early trials, although Roche’s has more shown promise recently.

Dive Insight:

Gilead’s investment increases its stake in Arcus from 20%. The California-based drugmaker also gets three seats on Arcus’ board, up from two, and won “governance enhancements enabling streamlined decision-making and reflecting the continued growth of the collaboration,” according to a Monday evening statement.

For Arcus, the deal adds one year’s worth of funding, exending its cash runway into 2027. It also will provide the resources to fund research on drugs that aren’t partnered with Gilead.

Drugmakers have looked at TIGIT as a promising new immune pathway to build on the cancer-fighting power of the PD-1 targeting drugs like Merck’s Keytruda and Bristol Myers Squibb’s Opdivo.

PD-1 is a “checkpoint” expressed on immune cells that can forestall the body’s response to cancer cells. Blocking it can help those immune cells find and attack a tumor. TIGIT is also associated with suppression of the body’s immune response, and researchers have hoped inhibiting its activity would similarly aid in checking cancer’s growth.

So far, drugmakers have largely tested TIGIT drugs in combination with PD-1 agents, but with mixed results. Recent Roche data in combination with the approved PD-L1 drug Tecentriq suggested promise in non-small cell lung cancer. On the other hand, Merck reported that a coformulation of Keytruda plus its experimental TIGIT-targeting drug failed to improve on chemotherapy in late-stage patients.

In announcing the deal, Gilead and Arcus said they will end a trial called ARC-10 that was testing domvanalimab and zimberelimab in lung cancer, instead favoring studies of those two immunotherapies on top of chemo.

After speaking with Arcus executives, Cantor Fitzgerald analyst Li Watsek wrote in a note to clients that the “decision to discontinue ARC-10 was not based on internal data of any kind, and was strategic in nature to better reallocate resources” to the chemotherapy combination trials.

However, Watsek added, “we expect investors to raise questions around clinical risks, given a lack of clinical data supporting the triplet regimen” of the two immunotherapies plus chemo.

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