Merck Confirms MK-1484 Removal From Pipeline After Trial Halted in 2024
Key Facts
Merck confirmed it had removed MK-1484, a drug candidate developed in partnership with Sutro Biopharma, from its research program, in a report published by Fierce Biotech on 6 November 2026. Merck said the decision came as part of a "routine pipeline-prioritization review," explaining the termination the company announced without establishing that the decision was made on that date. Sutro had disclosed in November 2024 that Merck notified it in August of that year of its decision to halt the clinical trial. Thus, confirmation that the program had been removed in 2026 came two years after the trial stopped, while the earlier notice was tied to portfolio-strategy considerations. The decision brings renewed attention to a collaboration between the two companies that began before the drug entered human trials.
Merck and Sutro announced their collaboration in 2018 to develop immuno-oncology and autoimmune-disease therapies. The agreement provided for the use of Sutro's cell-free protein synthesis and site-specific conjugation platforms under a collaboration and licensing arrangement between the parties. Sutro received an upfront payment of 60 million dollars and was eligible for milestone payments totaling up to 1.6 billion dollars, in addition to tiered royalties on sales. These terms place the program's potential value within a broader collaboration arrangement, but do not mean the maximum milestone payments were achieved. MK-1484 was one of the candidates to emerge from this joint research effort.
MK-1484 entered clinical development in 2022, with a Phase 1 study beginning in patients with advanced or metastatic solid tumors. The study tested the drug both on its own and in combination with pembrolizumab, Merck's drug marketed under the name Keytruda. Sutro said when the trial began that the first patient had been dosed and that it had earned a 10 million dollar milestone payment from Merck for reaching that milestone. The payment was tied to the study's start in 2022, not the termination decision that Sutro was notified of later. In August 2024, Merck notified the company of its decision to halt the trial, citing portfolio-strategy considerations, according to Sutro's disclosure filed on 13 November 2024.
The decision's context extends to other programs in Sutro's pharmaceutical collaborations. In its 2025 annual report, the company said its partners had ended further clinical development of candidates resulting from its collaborations with Merck, BMS and EMD Serono, after Phase 1 studies. The disclosure places the MK-1484 program among a group of candidates that did not advance to later clinical stages in those partnerships, according to Sutro. The annual report does not specify separate dates for ending development of each candidate in that statement. It does show, however, that ending MK-1484's development was not the only development of its kind in the Sutro collaborations mentioned.
According to Fierce Biotech, Merck no longer lists any assets targeting IL-2 in its pipeline after discontinuing MK-1484. The report also noted that the company had discontinued an IL-2-targeting candidate for autoimmune diseases in the previous year. This means the latest decision removed the other asset listed under this therapeutic target, according to the report's description of the pipeline when it was published on 6 November 2026. The report provides no details of a replacement IL-2 program at Merck. This picture remains tied to what the company listed in its research pipeline on that date.
In trading on 6 November 2026, Merck shares closed at 146.73 dollars, while Sutro Biopharma shares ended the session at 9.62 dollars. These prices provide the two stocks' closing levels in the same session on which the report covered Merck's confirmation that it had removed the program. The closing data provided do not include a comparison with a previous session or a measure directly linking either stock's movement to the MK-1484 decision. According to the available timeline, the decision to halt the trial dates to August 2024, while confirmation that the program had been removed featured in a November 2026 report. The news thus brings together the end of a clinical trial announced two years ago and later confirmation that the drug was no longer part of Merck's program.