With $117M in fresh cash, Amunix paves path to the clinic for ‘universal mask’ prodrug on the hunt for HER2 tumors

Despite all the excitement over the possibility of T cell therapies to crack the code against solid tumors, early safety data have limited the burgeoning field’s promise. A clutch of players hope to solve that problem by “masking” their drugs, and now one of those outfits has snared fresh investor cash to take its shot in the clinic.

Amunix closed a $117 million Series B to guide AMX-818, a masked protease-activated T cell engager for HER2 expressing tumors, to the clinic as well as shepherding its bustling pipeline of tumor hunters through the preclinical stage, the company said Thursday.

A 15-year-old firm that only recently pivoted its drug half-life extending platform into next-gen oncology development, Amunix is one of a suite of companies using masking antibodies to sneak therapies directly into the tumor microenvironment without the serious safety risks common to other immunotherapies.

What separates Amunix from the pack? For one, the biotech is using a “universal mask” for its immunotherapy drugs, CEO Angie You told Endpoints News, which allows the team to “plug and play” against different targets where other companies are forced to design custom cloaks for each target.

“The target universe is huge, and our strategy is ‘look, we’re not limited by good targets,'” You said.

The biotech’s lead candidate, for instance, targets HER2 — a highly validated and commonly targeted growth factor protein — but Amunix is also testing four additional candidates “in parallel” to target TROP2, PSMA and EGFR, You said. Those programs are less developed, but Amunix still plans to nominate a second candidate for human testing by the end of the year, she added.

The first immediate milestone for You’s team is taking AMX-818 into the clinic. Amunix will initially launch its first human trial in Spain and is scoping a CTA submission with the EMA by the end of the year to enable patient enrollment by early 2022, You said.

Going after HER2 is a bit of a double-edged sword: It’s a highly validated target but one with a ton of established competition. But You argued all of those drugs target tumors with high expression of HER2, leaving an untapped market in patients with low- or mid-HER2 expression that are “overexpressed” or amplified.

“Some people have a knee jerk reaction like ‘it’s so crowded,'” You said. “What’s emerging is a lot of institutions are screening their patients for HER2 because it seems to be a mechanism of reaction. We think there’s a lot of opportunity there.”

In mouse data presented in December, AMX-818 spurred complete responses even for tumors with low HER2 expression. That could offer a clue that AMX-818’s high potency will offer a clinical benefit across the HER2 spectrum, You said.

But it’s not just T cell engagers on Amunix’s docket. The biotech is also chasing a program for masked, protease-activated cytokines that avoid T cells altogether. That program is still “really early,” You said, but could offer a novel path to cutting down tumors.

With so much in the works, Amunix will look to greatly expand its team of 50 based in South San Francisco, You said. The biotech is also working on partnered drugs with Sanofi and 9 Meters, including a Factor VIII clotting drug with the French drugmaker that is currently in Phase III.

Thursday’s round was led by Viking Global Capital and joined by new investors in Bain Capital Life Sciences, BlackRock, Franklin Templeton, Janus Henderson Investors, ArrowMarkPartners, Avidity Partners, Clough Capital, and CaaS Capital Management. Existing investors that jumped on board the new round included Redmile Group, Venrock, Casdin Capital, Omega Funds, Frazier Healthcare Partners, Longitude Capital and Polaris Partners.

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