Current Market Outlook

Kalshi traders see a 76% chance that the FDA will approve Zidesamtinib (NVL-520) in 2026. That is a strong vote of confidence. A 76% probability means the market expects approval as the base case, with roughly a one-in-four chance something goes wrong. This is not a slam dunk, but it is well above the 50% threshold that signals genuine uncertainty.

The market resolves to Yes for full or accelerated approval. It resolves to No for a denial (CRL), sponsor withdrawal, conditional approval, or no decision at all.

Key Factors Driving the Odds

Zidesamtinib targets ROS1-positive non-small cell lung cancer, a mutation found in roughly 1-2% of NSCLC patients. The drug is a next-generation ROS1 inhibitor designed to overcome resistance to existing therapies like entrectinib and crizotinib, and to cross the blood-brain barrier more effectively.

Early clinical data from the Phase 1/2 ARROS-1 trial showed a 58% confirmed objective response rate in TKI-naive patients and 49% in patients previously treated with one ROS1 TKI. Intracranial response rates were also strong. These numbers are competitive with approved drugs and suggest a clear path to accelerated approval.

Nuvalent completed a rolling NDA submission in mid-2024 and received Breakthrough Therapy designation from the FDA. That designation alone signals the agency sees the drug as a potential improvement over existing options, which historically correlates with higher approval rates.

What Could Change These Odds

The biggest risk is the durability of response data. If the FDA demands longer follow-up before granting accelerated approval, the 2026 timeline could slip into 2027. That would trigger a No resolution under the current market terms. The Phase 2 portion of ARROS-1 is still enrolling, and mature progression-free survival data may not be ready by the time the FDA reviews the application.

Another risk is a surprise safety signal. Zidesamtinib has shown a favorable safety profile so far, with low rates of treatment-related discontinuation. But rare adverse events can emerge in larger datasets. If the FDA identifies a toxicity concern that requires additional studies, the approval odds drop sharply.

The competitive landscape matters too. Bristol Myers Squibb's repotrectinib already holds approvals in this space. If new data shows repotrectinib outperforming Zidesamtinib in head-to-head comparisons, the FDA could take a harder look at the benefit-risk balance. But that scenario is unlikely to derail approval entirely, given the unmet need for patients with brain metastases and resistance mutations.