recently announced the termination of its collaboration agreement with Japanese pharmaceutical company Kyowa Kirin regarding rocatinlimab, a candidate drug for autoimmune diseases.

Five years ago, Amgen paid a $400 million upfront payment and committed to milestone payments of up to $850 million to acquire the global (excluding Japan) rights to develop, manufacture, and commercialize rocatinlimab.

According to a press release from Kyowa Kirin, the termination of this agreement was based on Amgen's strategic priorities regarding its product portfolio . Kyowa Kirin will regain global rights to rocatinlimab.

Rocatinlimab (AMG451/KHK4083) is a blocking OX40 antibody with ADCC activity developed by Kyowa Kirin .

Previously, rocatinlimab met all co-primary and key secondary endpoints in two Phase 3 clinical trials for atopic dermatitis (AD), ROCKET-IGNITE and ROCKET-HORIZON, including skin clearance rate, which met the requirements for US regulatory filing.

In the ROCKET-IGNITE study, 42.3% and 36% of patients receiving 300 mg and 150 mg every four weeks, respectively, achieved EASI-75 (eczema area and severity index improvement of more than 75%) at week 24, significantly better than the placebo group (13%). The proportion of patients achieving “complete clearance” or “near clearance” (0 or 1) on the vIGA-AD score was 24% and 19%, respectively (compared to 9% in the placebo group). A consistent trend of advantage was also observed in the ROCKET-HORIZON study.

Although trial data showed that the drug was more effective than placebo, it did not show any advantage in cross-trial comparisons with Sanofi and Regeneron's blockbuster drug Dupixent (dupilumab).

William Blair analysts therefore concluded that rocatinlimab could only be used as a second-line treatment, with a "moderate" commercial prospect. This may be the key reason why Amgen abandoned the drug.

However, Kyowa Kirin has not given up on the further development of rocatinlimab . The company plans to submit a marketing application for the indication of atopic dermatitis to the FDA in the first half of 2026.

It is worth mentioning that Sanofi's similar OX40 candidate drug, amlitelimab, has also repeatedly encountered setbacks.

In its 2025 financial report, Sanofi discontinued Phase 2 development of the drug for the treatment of alopecia areata, celiac disease, and systemic sclerosis. In October 2025, it also terminated Phase 2 development for hidradenitis suppurativa. However, Sanofi is actively pursuing development for the AD indication.

According to data from the Phase 3 COAST1 study released by Sanofi, amlitelimab demonstrated durable efficacy and the potential for extended dosing intervals in adult patients with moderate to severe atopic dermatitis. In both treatment groups, a sustained upward trend in efficacy was observed throughout the treatment period without a plateau. However, it did not meet market expectations, and its efficacy level did not show an advantage over Dupixent in a non-head-to-head comparison.

Conclusion

OX40 is a T-cell co-stimulatory receptor, and its mechanism of action is similar to the "accelerator" of the immune system. Early research targeting OX40 mainly focused on the field of oncology, but progress was repeatedly hampered. Subsequently, new hope was ignited in the field of autoimmune diseases.

However, with the release of data from Sanofi's amlitelimab and Kyowa Kirin's rocatinlimab, neither has shown an advantage over the classic best-selling autoimmune drug Dupixent in the AD field. But this does not signify a complete defeat for the OX40 target; its advantages lie in its long-acting mechanism of action and its potential for combination therapy. Several second-generation OX40 drugs are currently in the research and development stage.

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