Fresh from IPO, Acelyrin's lead drug fails clinical trial

Acelyrin has been flying high in the wake of an unusually large initial public offering (IPO) in May, but came down to earth with a bump today after a failed clinical trial poleaxed its share price.

Top-line results from a phase 2 trial of lead drug izokibep in inflammatory skin disorder hidradenitis suppurativa (HS) showed no significant improvement over placebo for the IL-17A inhibitor.

Izokibep remains in clinical testing for other indications, including psoriatic arthritis (PsA) and uveitis, but the failure in its first major readout spooked investors, and Acelyrin's shares plunged around 57% in pre-market trading.

Acelyrin co-founder Shao-Lee Lin, formerly chief scientific officer at Horizon Therapeutics, said that the study did show some "consistent early and high orders of response for patients" with HS and a good safety and tolerability profile.

Izokibep was unable to show a statistically significant improvement over placebo on the primary endpoint in the study – a 75% improvement on the Hidradenitis Suppurativa Clinical Response scale (HiSCR75) – which was achieved by 39% of patients taking a weekly dose of the drug, 36% of those on a biweekly dose, and 29% of the placebo group.

The numbers looked slightly better for the 100% improvement rating (HiSCR100), with the weekly dose achieving that outcome in 26% of subjects, versus 22% for biweekly dosing and 12% for placebo, but also did not reach statistical significance.

Lin said the HiSCR100 results and earlier data in PsA "continues to demonstrate the potential of izokibep for resolution of disease, especially in difficult-to-treat tissues," and reiterated the company's commitment to pressing ahead with the weekly dose format across all three of its target indications.

Izokibep is smaller than other biologics in the IL-17 class, which includes blockbusters like Novartis' Cosentyx (secukinumab), and Acelyrin has long held that this will allow it to penetrate more deeply into tissues, potentially improving efficacy.

The next major readout for izokibep will come early next year from a phase 2b/3a trial in PsA, which is the largest indication for the drug. It should also report clinical data on a second clinical candidate, anti-IGF-1R antibody lonigutamab for thyroid eye disease, around the same time.

Acelyrin raised $540 million from its IPO, the largest for a biotech company since 2021, debuting its shares at $18. They swiftly rose to a high of almost $28, but were down just above $12 at the time of writing. It is still well funded, with cash reserves of around $823 million at the end of June.