Biopharmaceutical company Pharming Group N.V. (Euronext Amsterdam:PHARM) (NASDAQ:PHAR) on Wednesday reported positive topline Phase II trial results for leniolisib in genetically identifiable primary immunodeficiencies (PIDs) with immune dysregulation linked to altered PI3K delta signalling.

The findings were presented at the European Society for Immunodeficiencies (ESID) biennial meeting in Maastricht, the Netherlands.

The open-label study enrolled 13 participants with genetic variants in CTLA4, SOCS1, NFKB1 or FAS, nine of whom also had common variable immunodeficiency (CVID). After 20 weeks of treatment, leniolisib was generally well-tolerated, with no new safety signals identified and all treatment-related adverse events classified as Grade 1.

Among 11 evaluable participants, mean spleen volume decreased by 26.4%, while all four participants assessed for lymph node changes showed reductions, averaging 33.7% in index lesion size. Participants with impaired baseline gas exchange recorded a mean 8% improvement in predicted lung diffusing capacity, and lung disease scores improved in four of five evaluable participants. Liver stiffness also improved in two of three participants with elevated baseline measurements.

One participant discontinued treatment following acute hepatitis, while two others experienced serious adverse events deemed unrelated to leniolisib. All 12 participants who completed the study elected to enter a three-year extension study.

The findings provide initial clinical evidence of potential benefits beyond activated PI3K delta syndrome (APDS), for which leniolisib is approved in multiple countries. Pharming is evaluating the drug for additional immune disorders, including CVID, although its safety and efficacy for these investigational uses have not been established.

The company estimates that genetically identifiable PIDs and CVID associated with immune dysregulation represent a broader potential patient population than APDS, with estimated prevalence rates of approximately 7.5 and 39 patients per million, respectively, compared with 1.5 patients per million for APDS. The estimates for genetic PIDs and CVID include overlapping populations.