The First PROTAC Drug Got Approved. Then Nobody Wanted to Sell It.

By early June 2025, Arvinas CEO John Houston was telling investors the quiet part out loud. The opportunity was "smaller" than expected. It "doesn't move the dial for Pfizer" under a 50/50 structure. And honestly, it wasn't great for Arvinas either; they'd still be on the hook for half the commercial costs in a niche market.

Picture two people who bought a restaurant together expecting it would be the next Cheesecake Factory, then realizing it's more of a beloved neighborhood bistro. Still good! Just not what you architected a partnership around.

Enter Rigel: The Goldilocks Partner

On May 12, 2026, Arvinas and Pfizer announced they'd licensed Veppanu's global rights to Rigel Pharmaceuticals. The structure is clean.

Rigel gets: exclusive worldwide rights to develop, manufacture, and sell Veppanu. They run the U.S. launch and can sublicense outside the country.

Arvinas and Pfizer get: $70 million upfront, plus $15 million tied to transition milestones (split evenly between them). On top of that, up to $320 million in future milestone payments and tiered royalties in the mid-teens to mid-twenties percent on net sales. All split 50/50.

Rigel also kicks in up to $40 million over four years toward ongoing development costs, while Arvinas and Pfizer finish their existing clinical work.

Why Rigel? Because what looks like a niche product for Pfizer looks like a flagship for a $275 million revenue company. Rigel already sells three oncology and hematology drugs (Tavalisse, Rezlidhia, and Gavreto) through a specialty sales force that calls on the exact same oncologists who treat breast cancer. For them, adding Veppanu is like a food truck adding a second menu item: same kitchen, same customers, way more revenue.

Rigel has described Veppanu as a major focus to accelerate revenue growth and a meaningful driver of long-term growth.

A Crowded Dance Floor

Veppanu isn't walking into an empty room. The ESR1-mutated breast cancer space has gotten competitive fast.

Elacestrant (Orserdu), approved in early 2023, was the first oral option specifically for ESR1-mutated disease. It got there first, but its efficacy bar is moderate. Then came imlunestrant (Inluriyo) from Eli Lilly, approved in September 2025, which showed a 38% reduction in disease progression risk and comes bundled with an abemaciclib combination strategy. AstraZeneca's camizestrant has Breakthrough Therapy designation and strong Phase 3 data. Roche's giredestrant combined with everolimus showed a striking 62% risk reduction in ESR1-mutated patients.

Veppanu's edge is its mechanism: it's the only PROTAC in the group, degrading the estrogen receptor rather than just blocking it. Whether that translates into a durable commercial advantage will depend on real-world outcomes, combination data, and (frankly) how well Rigel executes the launch.

Why This Deal Matters Beyond Breast Cancer

Forget the specific dollar amounts for a second. The bigger story is what this deal signals for an entire class of drugs.

PROTACs have been the darling of biotech conferences for years, promising to drug the "undruggable" by destroying disease proteins rather than merely inhibiting them. But conference slides don't pay the bills. Commercial proof does.

Veppanu's approval was the scientific milestone. This Rigel deal is the commercial one. It shows that a PROTAC drug can find a viable path to market, even when the initial commercial blueprint falls apart. The template here (platform innovators hand off to specialized commercial partners) could become the default playbook for future degrader drugs.

For Arvinas, the deal also frees up resources and attention for the rest of their PROTAC pipeline. For Pfizer, it clears an awkward line item off the books. And for Rigel, it's a bet-the-company moment disguised as a licensing deal.

The Bottom Line

The first approved PROTAC nearly stumbled at the finish line, not because the science failed, but because the business model didn't match the market. It took a three-way restructuring and a smaller, hungrier partner to fix it.

The drug works. Now we'll find out if the deal does too.

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