Merck Drops IL-2 Cancer Candidate MK-1484
The discontinued research-stage drug was tested alone and with Keytruda in solid tumors.
Updated on Nov. 6, 2026 in Biotech
Merck has discontinued MK-1484, an IL-2 agonist developed with Sutro Biopharma and tested in patients with advanced or metastatic solid tumors. The program is research-stage: it was in clinical testing but has now been dropped, so it will not reach patients.
Why it matters
The decision removes Merck's IL-2 assets from its pipeline, following its earlier scrapping of an autoimmune-focused IL-2 mutein. It signals that the company is narrowing its bets on IL-2 signaling in cancer and immune disease.
MK-1484 is an IL-2 agonist, a protein designed to stimulate immune T cells, built using Sutro's cell-free protein synthesis and site-specific conjugation platforms. The source reports no efficacy or dosing figures for the drug.
The players
Merck & Co.
A global pharmaceutical company whose oncology franchise includes the checkpoint inhibitor Keytruda, and which has now dropped its IL-2 assets.
Sutro Biopharma
A biotechnology company whose cell-free protein synthesis and site-specific conjugation platforms were used to build MK-1484 in its 2018 collaboration with Merck.
The details
MK-1484 was developed under a 2018 collaboration between Merck and Sutro Biopharma, which used Sutro's cell-free protein synthesis, a method of producing proteins outside living cells, and site-specific conjugation, a technique for attaching molecules at precise positions on a protein. The companies moved the drug into the clinic in 2022, testing it alone and alongside Keytruda, Merck's checkpoint inhibitor, in patients with advanced or metastatic solid tumors. Merck has now scrapped the program, describing the move as part of a routine pipeline prioritization.
Timeline
2018: Merck and Sutro begin the collaboration that produced MK-1484.
2022: MK-1484 enters clinical trials.
Last year (2025): Merck scraps an autoimmune-focused IL-2 mutein.
This week (November 2026): Merck confirms MK-1484 has been discontinued.
The Tech Race
Merck's decision leaves Bristol Myers Squibb, which pursued IL-2 through its Nektar Therapeutics deal, as a prominent competitor in this approach. The discontinuation narrows the field of companies still developing IL-2 therapies from the Merck side.
Patients with solid tumors will not receive MK-1484 as a treatment, and the combination trial with Keytruda is no longer ongoing. The source gives no timeline for any replacement therapy.
The takeaway
The discontinuation shows drug developers pruning IL-2 programs even after clinical entry. Watch for Bristol Myers Squibb's Nektar-linked IL-2 work to see whether the approach continues to advance in the clinic.
Further reading
Explore more Biotech developments shaping drug pipelines in the United States.
Source note: This article includes information reported by FierceBiotech - free daily biotech briefing.
