IMNM Varegacestat NDA Accepted: Desmoid Tumor PDUFA Apr 2027

The FDA accepted Immunome’s (IMNM) New Drug Application for varegacestat on July 8, 2026, setting a PDUFA target action date of April 28, 2027. Varegacestat is an oral, once-daily gamma-secretase inhibitor for adults with progressing desmoid tumors, a rare soft tissue tumor type with no FDA-approved therapies.

The numbers

• Ticker: IMNM
• Stock price: $22.58 (close July 25, 2026)
• Market cap: $2.56 billion
• Drug: Varegacestat (formerly AL102), an oral gamma-secretase inhibitor
• Indication: Adults with progressing desmoid tumors
• Trial: RINGSIDE Phase 3 (n=156, global, randomized, double-blind, placebo-controlled)
• PDUFA date: April 28, 2027

The RINGSIDE trial met its primary endpoint with an 84% reduction in the risk of disease progression or death versus placebo (hazard ratio 0.16, 95% CI 0.071 to 0.375, p<0.0001). The confirmed objective response rate was 56% with varegacestat versus 9% with placebo. In an exploratory analysis, the median best change in tumor volume was negative 83% with varegacestat versus positive 11% with placebo. The trial also met all key secondary endpoints, including statistically significant improvements in tumor volume reduction and worst pain intensity.

The disease

Desmoid tumors are aggressive, non-metastatic soft tissue tumors that are prone to recurrence. Approximately 1,000 to 1,650 people are diagnosed each year in the US, with 10,000 to 11,000 actively managed patients. The tumors cause debilitating pain, deformity, and in some cases life-threatening organ damage. Although not considered cancerous, they often require systemic treatment to prevent permanent disability. Current options are limited to surgery, radiation, and off-label drugs including sorafenib, methotrexate, and NSAIDs, none approved specifically for desmoid tumors.

The mechanism

Varegacestat works by inhibiting gamma-secretase, an enzyme that activates the Notch signaling pathway. In desmoid tumors, mutations in the beta-catenin gene drive aberrant Wnt signaling, and gamma-secretase inhibition disrupts the downstream signaling cascade that promotes tumor growth. The gamma-secretase inhibitor class was previously studied in Alzheimer’s disease, where it failed due to cognitive side effects from disrupting Notch signaling in the brain. In desmoid tumors, the mechanism targets the pathway driving tumor proliferation, and the safety profile is manageable for a non-malignant condition.

The most common adverse events in the RINGSIDE treatment arm were diarrhea (82%), fatigue (44%), rash (43%), nausea (35%), and cough (34%). Most events were grade 1 or 2.

The company

Immunome, originally focused on antibody-drug conjugates, has diversified into rare tumors with varegacestat. The company is also developing ADCs for oncology, making varegacestat one of several pipeline assets. A European Marketing Authorization Application is planned by the end of 2026.

What to watch

The risk is the safety profile. Gamma-secretase inhibitors have a history of off-target effects from Notch pathway inhibition, and the FDA will scrutinize whether the 82% diarrhea rate and other adverse events are acceptable for a non-malignant tumor type. The 275-day runway to the PDUFA date is long; watch for any FDA information requests or advisory committee scheduling in the coming months. Also watch for competitive developments: Ogsiveo (nirogacestat), SpringWorks Therapeutics’ gamma-secretase inhibitor, was approved for desmoid tumors in 2023, meaning varegacestat would not be first in class but would compete on efficacy and convenience. The 56% ORR in RINGSIDE is the highest reported in a Phase 3 desmoid tumor trial, which could differentiate it if the label is clean.

Sources: Immunome NDA acceptance press release, RINGSIDE Phase 3 results, what is a PDUFA date

What It Means for the Trade

Varegacestat enters a market SpringWorks already opened, so the trade is a head-to-head on label quality — and RINGSIDE’s numbers give Immunome real ammunition: an 84% risk reduction (hazard ratio 0.16), a 56% confirmed ORR against 9% placebo, and a median best tumor-volume change of negative 83%. If those hold up against Ogsiveo’s registrational profile, varegacestat can win the efficacy-and-convenience argument as a once-daily oral in a field where response depth drives prescribing. The catalyst calendar is long — the April 28, 2027 PDUFA is the binary, with an EU MAA planned by end of 2026 as the parallel track — and the interim months trade on regulatory signals: FDA information requests, adcomm scheduling, or the silence that usually precedes a standard review. At a $2.56 billion market cap, Immunome is pricing in approval plus a competitive launch, so the position-sizing question is whether a second-to-market desmoid drug can generate the share the valuation implies when the incumbent has three years of physician relationships.

Mechanism and Market Context

Gamma-secretase is the enzyme that cleaves Notch receptors into their active signaling forms; in desmoid tumors, where beta-catenin mutations drive aberrant Wnt signaling, Notch appears to function as a pro-survival amplifier, and cutting the cleavage step shuts down the growth signal. The class history is the cautionary backdrop: gamma-secretase inhibitors failed in Alzheimer’s precisely because chronic Notch disruption in the brain produced cognitive toxicity — but in desmoid tumors, that same pathway interruption is the therapeutic point, and a manageable grade 1-2 profile clears the bar for a non-malignant disease. The RINGSIDE side-effect profile (82% diarrhea, 44% fatigue) mirrors the class and will be the label’s centerpiece discussion.

Risks and What Could Go Wrong

1. The FDA may balk at the 82% diarrhea rate for a non-malignant indication, or attach a REMS-style restriction that blunts launch.
2. Second-to-market against an entrenched Ogsiveo means share gains must come from switching, a slower and costlier revenue ramp than first-in-class enjoyed.
3. The 275-day review runway invites information requests and possible adcomm delay risk before April 2027.
4. Immunome’s valuation bundles ADC-pipeline optionality with this approval; a desmoid stumble drags the whole story, since neither asset has revenue yet.