H.C. Wainwright downgraded Summit Therapeutics PLC's stock rating from Buy to Neutral on May 22, removing its prior $23 price target. This action was prompted by positive Phase III data for sac-TMT, an antibody-drug conjugate developed by Merck and Kelun-Biotech for lung cancer treatment, raising competitive concerns.

The primary reason for the downgrade is H.C. Wainwright's apprehension over the competitive pressure sac-TMT data may exert on Summit's core drug, ivonescimab. According to an abstract presented at the ASCO 2026 meeting, sac-TMT combined with Keytruda for first-line treatment of PD-L1-positive non-small cell lung cancer significantly reduced the risk of disease progression or death by 65%, with an objective response rate exceeding 70%, compared to 42% for the Keytruda monotherapy group.

H.C. Wainwright noted that the favorable early survival trends demonstrated by the sac-TMT dataset raise the competitive bar. Furthermore, Summit's delay in providing more mature overall survival update data from its HARMONi-2 trial introduces incremental risk to the stock. The firm believes Summit's near-term catalysts may be insufficient to revitalize the stock's performance.

It is noteworthy that Summit's own HARMONi-3 trial recently faced a setback. An interim analysis released in late April showed that ivonescimab combined with chemotherapy did not achieve statistical significance for progression-free survival in patients with squamous non-small cell lung cancer, causing the company's stock to plummet over 25% in a single day. Stifel analyst Dara Azar indicated that the sac-TMT data does not pose a direct threat to ivonescimab's competitive positioning, though H.C. Wainwright clearly maintains a more cautious stance.

Additionally, Bernstein initiated coverage of Summit on the same day, assigning an Underperform rating with a $7.70 price target. The rationale cited includes the company's high concentration on the single product ivonescimab and the risk that multiple key Phase III clinical trials may fail to achieve statistical significance. Summit currently has no marketed drugs, reported an EBITDA loss of $1.22 billion over the past twelve months, and remains in a sustained loss-making position.