A Nektar Therapeutics drug has met the skin clearance goals of a closely watched mid-stage clinical trial in atopic dermatitis. While these preliminary results bring validation to the therapy’s novel approach to the immune response driving the disease, analysts note the market for atopic dermatitis drugs is crowded and it’s unclear whether Nektar’s drug can stand out, particularly against a blockbuster Sanofi product whose approvals include atopic dermatitis.
The placebo-controlled Phase 2b test evaluated three doses of the Nektar drug, rezpegaldesleukin (rezpeg for short), in 393 patients with moderate-to-severe atopic dermatitis, also called eczema. The main goal is measuring the change in score according to scale used to assess disease severity — the higher the score, the more severe the disease. San Francisco-based Nektar said Tuesday that all three doses of its drug showed statistically significant changes in score at 16 weeks. The greatest improvement was shown by the high-dose group, which posted a 30% placebo-adjusted reduction in score.
Rezpeg is a biologic drug designed to target the interleukin-2 (IL-2) receptor complex, stimulating the proliferation of regulatory T cells (Tregs), a type of immune cell that dampens excessive immune responses. This approach is intended to bring the immune system back into balance. That’s different than other biologic drugs that work by blocking certain proteins or pathways associated with inflammation. Sanofi and Regeneron Pharmaceuticals’ Dupixent is an antibody designed to block the IL-13 and IL-4 pathways. The blockbuster product is currently the top biologic medicine for atopic dermatitis.
Cross-trial comparisons have limitations, but it’s hard to avoid them when a drug candidate aims to go up against the top product in an indication. Dupixent’s Phase 2b results in atopic dermatitis showed a placebo-adjusted 50% average reduction in score at 16 weeks. William Blair analyst Andy Hsieh pointed out in a research note that achieving 75% or greater improvement from baseline measures is a key measure from a regulatory standpoint. Rezpeg’s scores for the middle and high doses both fall well short of Dupixent’s marks on this measure.
Rezpeg may also be disadvantaged from a tolerability standpoint. While Nektar reported that its drug was safe and well tolerated with the most common adverse event being injection site reactions, Hsieh noted rezpeg posted higher rates of these reactions in its test compared to the results from Dupixent’s study.
“We believe the relatively high rates of injection site reactions observed for rezpeg could serve as a headwind in the absence of clearly differentiating efficacy data,” Hsieh said.
The preliminary rezpeg results announced Tuesday are from the 16-week induction period of its Phase 2b test. Patients are continuing in a 36-week maintenance portion of the study; data from this part are expected in the first quarter of 2026. Nektar believes this drug has the potential to address other immunological disorders. A Phase 2b test in alopecia areata is expected to post preliminary data in the fourth quarter of this year.
The rezpeg results sent Nektar’s stock price soaring, opening Tuesday at $20 per share — more than double Monday’s closing price. Hsieh acknowledged the jump in Nektar’s stock price, but he characterized it as a “valuation normalization event” rather than investors ascribing value to a differentiated asset. He noted that Nektar shares trade around the company’s current cash levels, which the company reported was about $220.7 million at the end of the first quarter of this year. Hsieh added that he’s looking for more data updates to further demonstrate rezpeg’s therapeutic effect, which could boost the asset’s competitive profile.
Rezpeg is Nektar’s most advanced program. The drug is wholly owned by the biotech, but it wasn’t always that way. In 2017, Eli Lilly paid $150 million up front to begin a partnership on rezpeg. Lilly terminated the alliance in 2023 following disappointing clinical trial results. Months later, Nektar sued Lilly for breach of contract, alleging its former partner miscalculated data in atopic dermatitis and psoriasis studies in order to favor an atopic dermatitis drug it had acquired from Dermira. That IL-13-blocking antibody, brand name Ebglyss, won FDA approval in atopic dermatitis last September. Meanwhile, Nektar’s litigation against Lilly is continuing.
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