Numab’s billion-dollar antibody deal takes an unexpected turn

Now the story has taken a different direction. Johnson & Johnson (J&J) has discontinued the clinical development of its atopic dermatitis candidate JNJ-95475939 (also known as JNJ-5939). The pharmaceutical group terminated a Phase IIb trial in patients with moderate to severe atopic dermatitis after a pre-planned interim analysis failed to meet the predefined efficacy criteria. The decision came just around ten months after the study began in February 2025.

In a year-end statement, J&J said the data did not reach the “high efficacy bar” the company applies when deciding whether to advance programmes in atopic dermatitis. Importantly, there were no safety concerns: the subcutaneously administered therapy was reported to be well tolerated. Detailed trial data have not yet been released.

An early end, but not the end of the story

The halt is also notable from a commercial perspective. J&J only acquired the asset in mid-2024, paying US$1.25 billion in cash to Numab Therapeutics for the bispecific antibody. The deal was underpinned by early clinical data and the expectation that a dual-acting antibody could outperform existing therapies. JNJ-95475939 targets the cytokines IL-4 and IL-31R, both at least for the basis of the cooperation seen as key drivers of inflammation in atopic dermatitis. Other experts in this medical indication would not support this opinion too much.

IL-4 is a well-established target already addressed by blockbusters such as Dupixent from Regeneron and Sanofi. IL-31, by contrast, has been viewed as a promising add-on target, particularly for controlling the intense itching associated with the disease. While standalone IL-31 approaches have so far delivered only moderate efficacy, Galderma’s antibody Nemluvio nevertheless secured FDA approval at the end of 2024. J&J’s ambition was to combine both targets in order to “break through the efficacy limitations of monotherapies”, as company executives had previously put it.

Despite the setback, J&J is keen to underline its continued commitment to inflammatory skin diseases. Attention is now shifting to other pipeline projects, including JNJ-7528, another atopic dermatitis candidate currently in Phase I and expected to move into Phase IIb testing in 2026. In addition, J&J strengthened its position in May 2024 with the US$850 million acquisition of Proteologix, gaining access to a bispecific antibody targeting IL-13 and TSLP, as well as an exclusive licence to a STAT6 programme from Japan’s Kaken Pharmaceutical — a familiar name as Kaken had previously collaborated with Numab on the original antibody programme.

Numab emerges unscathed

The early termination of JNJ-95475939 is a reminder of just how high the bar is in a fiercely competitive therapeutic area and how even billion-dollar bets on innovative mechanisms can falter once they meet clinical reality, despite encouraging early data. For Numab, however, little changes in practical terms. The company’s strategic focus on oncology remains intact and unaffected in terms of reputation.

In fact, Numab may emerge in an even stronger position than initially anticipated. With the programme discontinued, any potential downstream milestone payments that Numab would have owed to its former partner Kaken are no longer due. Sometimes, in biotech as elsewhere, stories do not unfold as expected and occasionally, taking a different turn still leads to a positive ending.