The OX40 monoclonal antibody has had a troubled history.

On March 3, Kylin Pharmaceutical announced that due to the addition of a new case of Kaposi's sarcoma in clinical trials, the company decided to discontinue all clinical studies of its OX40 monoclonal antibody Rocatinlimab.

This breaking news has once again thrust the OX40 monoclonal antibody into the spotlight.

Once, this was a promising new area of autoimmune medicine that industry giants had high hopes for. However, the results were less than satisfactory, forcing the market to re-evaluate the competitiveness of OX40 monoclonal antibody.

However, with the exposure of the risk of tumorigenesis, OX40 monoclonal antibodies may face more challenges in the field of autoimmune diseases.

01

Cancer Controversy

On March 3, a news release from Peking Union Medical College Hospital brought the OX40 monoclonal antibody into the spotlight.

Hsieh Ho Kirin stated that a recent safety review of Rocatinlimab revealed one new confirmed case and one suspected case of Kaposi's sarcoma, in addition to the one case already recorded.

The company stated that these confirmed cancer cases suggest a link to the OX40 pathway regulatory mechanism, and the press release further stated: "Based on this update, both Kyowa Kirin and Amgen have concluded that the potential risks of Rocatinlimab may outweigh the benefits for the patients studied." Subsequently, Kyowa Kirin announced the discontinuation of the Rocatinlimab study.

Although the causal relationship between OX40 and Kaposi's sarcoma is still unclear, it is hard to accept that a drug meant to treat the disease has become a carcinogenic factor.

This is not an isolated case; a Kaposi's sarcoma event also occurred in the ATLANTIS Phase 2 study with Amlitelimab. However, the company determined that the patient had known risk factors and has since discontinued Amlitelimab.

Although the results did not affect the progress of Amlitelimab, the new developments in Rocatinlimab have undoubtedly cast a further shadow over the OX40 monoclonal antibody.

02

Controversy over efficacy

This is not the first time Rocatinlimab has suffered a setback.

On January 30, 2026, Amgen and Kyowa Kirin announced the termination of their collaboration on the development and commercialization of Rocatinlimab. After paying $400 million and initiating eight Phase 3 clinical trials for AD, Amgen resolutely chose to abandon the project.

The reason is not hard to understand: the competitiveness of Rocatinlimab is controversial.

Indeed, Rocatinlimab has achieved success in a phase 3 clinical trial in the field of atopic dermatitis (AD). Clinical results showed that at week 24 of treatment, 54.1% and 52.3% of patients in the Rocatinlimab 150 mg and 300 mg groups, respectively, achieved EASI 75, which was a significant improvement compared to placebo.

However, in non-head-to-head cases, rocatinlimab shows no advantage in efficacy compared to dupilumab, and its safety issues are more prominent.

In the high-dose group of Rocatinlimab 300mg, 12% of patients experienced fever and 6% experienced chills, indicating frequent injection-related adverse reactions. Considering the limited future commercial prospects of the drug and potential safety issues, Amgen ultimately chose to terminate the collaboration to minimize losses.

The emergence of a series of problems does not mean that OX40 monoclonal antibodies have no future. However, how to find a breakthrough through molecular design, drug delivery strategies, or combination therapies is a question that more newcomers may need to consider.

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