AnaptysBio’s Experimental Therapy for Palmoplantar Pustulosis Fails in Phase 2 Trial

Rare Daily Staff

AnaptysBio reported that its phase 2 clinical trial of imsidolimab for the treatment of moderate-to-severe palmoplantar pustulosis failed to meet its primary endpoint.

Palmoplantar pustulosis (PPP) is a rare, recurrent inflammatory disorder in which affected individuals develop small to large sterile blisters filled with pustules on the palms of the hands and/or soles of the feet that can be painful. The exact cause of PPP is not known and it primarily affects women between 40 and 69 years of age, predominantly smokers. PPP is strongly related to psoriasis vulgaris, some patients have both PPP and plaque psoriasis or PPP and psoriatic arthritis. Available treatments include topical steroids or retinoids, light therapy, and systemic therapies for severe cases with immunosuppressants (methotrexate, cyclosporine) and/or biological therapies.

Imsidolimab, previously known as ANB019, is an antibody that inhibits the function of the interleukin-36-receptor, or IL-36R, which AnaptysBio plans to initially develop as a potential first-in-class therapy for patients suffering from generalized pustular psoriasis, or GPP, EGFR-mediated skin toxicity, ichthyosis, hidradenitis suppurativa and acne.

AnaptysBio does not expect to continue clinical development of imsidolimab for the treatment of PPP, but will continue its development in five other immuno-dermatological indications, including advancing it into a late-stage grail in GPP in mid-2021.

Fifty-nine PPP patients were enrolled in the POPLAR trial at 36 sites across the U.S. and Europe. Patients were washed out of prior PPP therapy and no concomitant therapy was permitted during the trial.   Key inclusion criteria included age between 18 and 75 years, clinically confirmed ongoing moderate-to-severe PPP disease history of at least 3 months, and active pustules on palms and/or soles upon enrollment. Patients were treated with a 200mg subcutaneous induction dose of imsidolimab at Day 1, followed by monthly 100mg subcutaneous doses on Days 29, 57 and 85. The primary endpoint of this trial was mean change in Palmoplantar Pustular Psoriasis Area Severity Index (PPPASI) at week 16 relative to baseline and the estimator for between-group comparison was LSMD.   Baseline clinical assessments were conducted for each patient on Day 1 prior to imsidolimab dosing. Missing data was modeled using mixed model for repeated measures (MMRM) methodology.  

Top-line results showed that treatment with imsidolimab treatment did not demonstrate statistically significant improvement over placebo in the PPPASI change from baseline at week 16, the primary endpoint. Imsidolimab was generally well tolerated and no serious or severe adverse events were reported in the drug arm of the trial.

“While the top-line results are disappointing, I would like to sincerely thank everyone involved in the POPLAR trial, including the patients, the investigators, their staff and our employees,” said Hamza Suria, president and CEO of AnaptysBio. “Imsidolimab is currently being advanced in 5 other immuno-dermatology indications and we look forward to multiple additional clinical readouts during 2021 and 2022.”

Photo: Hamza Suria, president and CEO of AnaptysBio