Imsidolimab treatment did not significantly improve over placebo.

An investigational antibody drug candidate failed to improve over placebo in a mid-stage trial in the rare skin condition palmoplantar pustulosis.

Palmoplantar pustulosis (PPP) is a rare chronic skin condition, characterised by blisters and pustules which can appear on the patients’ hands and feet. 

A Phase II trial of imsidolimab evaluating the drug for the treatment of moderate-to-severe PPP failed to meet its primary endpoint. 

Patients enrolled into the imsidolimab arm of the study had mean baseline Palmoplantar Pustular Psoriasis Area Severity Index (PPPASI) scores of 16. 

In the placebo group, patients had a mean baseline PPPASI score of 19, making the overall average score 18. 

For each arm, the mean baseline Palmoplantar Pustulosis Investigator Global Assessment (PPPIGA) was 3.1. 

For the primary endpoint of least-squares mean difference (LSMD) PPPASI improvement at week 16, imsidolimab failed to improve over placebo – with a score of 6.1 compared to 6.3 observed in each group, respectively. 

Imsidolimab-treated patients had a mean PPPASI change from baseline of 38% improvement, compared to 33% for placebo-patients. 

In addition, 38% of patients achieved 50% PPPASI improvement and 17% achieved 75% PPASI improvement in the imsidolimab group, compared to 50% and 13% on each responder threshold in the placebo arm. 

Although imsidolimab showed no statistically significant improvement over placebo on these measures, the drug was found to be well-tolerated with a similar frequency of adverse events between the treatment groups. 

Further clinical development of imsidolimab in PPP has been suspended, but the drug candidate will continue to be investigated in five additional immuno-dermatological indications. 

This includes generalised pustular psoriasis (GPP), EGFRi-mediated skin toxicity, ichthyosis, hidradenitis suppurativa and acne.