Kyowa Kirin Ends Late-Stage Rocatinlimab OX40 Development

In a move that surprised many in the dermatology community, Kyowa Kirin has announced it will discontinue all ongoing clinical trials of rocatinlimab, its investigational anti-OX40 monoclonal antibody.¹ The decision follows a recent safety review of the global development program conducted with partner Amgen.

Rocatinlimab had been under evaluation for moderate to severe atopic dermatitis (AD), prurigo nodularis, and moderate to severe asthma. Just weeks earlier, the company had reaffirmed its commitment to the molecule and signaled plans for regulatory submission in the first half of 2026.² Now, the program has been halted due to emerging safety concerns—specifically, cases of malignancy that raised biologic questions about OX40 pathway modulation.

“In a chronic disease like [AD], therapies must combine sustained benefit with a highly reassuring safety profile,” Christopher Bunick, MD, PhD, associate professor of dermatology at Yale School of Medicine in New Haven, Connecticut, and Dermatology Times editor in chief, said in an exclusive statement. “If efficacy is slower onset and the sponsor identifies malignancy concerns with possible viral or immune-related links, highlighted by Kaposi sarcoma, the benefit-risk balance can shift quickly.”

What Changed?

According to Kyowa Kirin, a planned safety update identified new concerns about malignancies with potential viral or immune-related links. Most notably, there was 1 new confirmed case and 1 suspected case of Kaposi sarcoma, in addition to a previously confirmed case.

“This is deeply disappointing news, as we had hoped to bring a safe and effective treatment to patients. Rocatinlimab has demonstrated durable and clinically meaningful efficacy in moderate to severe AD in the ROCKET program. However, the safety profile has evolved, and as patient safety remains our highest priority, we have taken this decisive and cautious step,” said Abdul Mullick, PhD, president and chief operating officer of Kyowa Kirin. “Although this outcome is not what we hoped for, our work has not been in vain. The knowledge gained from the program will contribute meaningfully to the broader understanding of the OX40 pathway and future research efforts.”

Although the overall number of malignancies reported across the entire development program remains below expected background rates, the characteristics of these cases were considered concerning enough to alter the benefit–risk assessment. The possibility of a mechanistic link to OX40 modulation—although not proven—could not be excluded.

“OX40/OX40L targeting has been explored as an upstream strategy in [AD] with the aim of modulating sustained T-cell activation and immune memory. The discontinuation of rocatinlimab underscores the importance of rigorous, long-term safety evaluation—and reinforces the need to balance mechanistic promise with careful safety assessment—when developing therapies that alter costimulatory signaling,” said Mona Shahriari, MD, FAAD, associate clinical professor of dermatology at Yale School of Medicine and associate director of clinical trials at CCD Research. “These findings add to our understanding of how best to approach immune recalibration in a complex, heterogeneous disease like AD.”

A Promising Run in AD

The discontinuation is particularly striking, given the strength of the phase 3 data in AD. In late 2025, results from the ROCKET-IGNITE (NCT05398445) and ROCKET-HORIZON (NCT05651711) trials were published in The Lancet. These studies enrolled nearly 1500 adults with moderate to severe AD and demonstrated that rocatinlimab monotherapy met all coprimary and key secondary end points. A significant proportion of patients achieved a revised Investigator Global Assessment score of 0 or 1, including stringent criteria limiting residual skin findings.³

For dermatologists, what made rocatinlimab especially compelling was its mechanism. By targeting OX40, a costimulatory receptor expressed on activated T cells, the drug aimed to “rebalance” pathogenic T-cell responses rather than simply block a downstream cytokine. This raised the possibility of more durable disease control—even extended dosing intervals.

Long-term extension data from ASCEND had suggested sustained responses, reinforcing optimism that OX40 modulation might represent a next-generation approach in AD.

Why OX40 Raised Eyebrows

OX40 plays a central role in T-cell activation, survival, and memory formation. Modulating this pathway theoretically dampens pathogenic T-cell populations involved in chronic inflammatory disease. However, it also intersects with immune surveillance mechanisms.

Kaposi sarcoma is a vascular tumor associated with human herpesvirus 8 and is classically linked to immune dysregulation. The emergence of confirmed and suspected cases in the program raised a biologically plausible concern that altering OX40 signaling could, in some patients, affect antiviral or antitumor immunity.

Importantly, causality has not been established. The total malignancy count was below background rates, but the pattern and tumor type prompted caution.

Impact on the Dermatology Landscape

For clinicians treating moderate to severe AD, rocatinlimab has been viewed as a potential differentiator in an increasingly competitive field. Biologics targeting IL-4/IL-13 and IL-13 alone, as well as Janus kinase inhibitors, have dramatically expanded options. Still, unmet needs remain, particularly for patients with partial responses, loss of efficacy, or concerns about chronic immunosuppression.

Rocatinlimab’s appeal was its upstream, T-cell–modulating approach and the prospect of longer disease control after limited dosing. Its discontinuation narrows the late-stage pipeline for novel mechanisms in AD.

The ripple effects may also extend to prurigo nodularis and asthma, where OX40-targeted strategies have been under active investigation.

What Happens Next?

Kyowa Kirin and Amgen are notifying investigators and regulatory authorities. Trial participants will complete required safety follow-up visits before studies are formally terminated. The companies plan a comprehensive analysis of the full data set and have committed to providing further updates once that review is complete.

For dermatologists, the rocatinlimab story is both disappointing and instructive. It highlights how even late-stage programs with strong efficacy data can shift course when safety signals emerge. At the same time, it adds important real-world knowledge about OX40 biology and immune modulation.

As the AD treatment armamentarium continues to evolve, the field will likely watch closely to see whether other OX40-targeted therapies proceed, as well as how future programs balance the promise of durable T-cell reprogramming with the need for long-term safety vigilance.

References

1. Kyowa Kirin announces discontinuation of rocatinlimab clinical trials. News release. Kyowa Kirin. March 3, 2026. Accessed March 3, 2026. https://www.globenewswire.com/news-release/2026/03/03/3248303/0/en/Kyowa-Kirin-Announces-Discontinuation-of-Rocatinlimab-Clinical-Trials.html
2. Kyowa Kirin to regain control of rocatinlimab development and
   commercialization program, demonstrating strong commitment to
   address high unmet medical need in atopic dermatitis. News release. Kyowa Kirin. January 30, 2026. Accessed March 3, 2026. https://www.kyowakirin.com/media_center/news_releases/2026/pdf/e20260130_01.pdf
3. Guttman-Yassky E, Kabashima K, Worm M, et al. Efficacy and safety of rocatinlimab for the treatment of moderate-to-severe atopic dermatitis in ROCKET-IGNITE and ROCKET-HORIZON: two global, double-blind, placebo-controlled, randomised phase 3 clinical trials. Lancet. 2026;407(10523):53-66. doi:10.1016/S0140-6736(25)01865-3