Pittsburgh, Pennsylvania-based Krystal Biotech (Nasdaq: KRYS) reported shrinkage of both injected and non-injected basal cell carcinoma (BCC) lesions in three patients with Gorlin syndrome treated with KB113. The preliminary findings suggest the investigational immunotherapy could have activity beyond the tumors directly treated, although the small, uncontrolled study cannot establish its effectiveness.
Gorlin syndrome is a genetic condition that predisposes patients to developing numerous BCCs over their lifetimes, often requiring repeated, potentially disfiguring surgical procedures. A treatment that also acts on non-injected lesions could potentially reduce that burden, but the pilot study did not establish whether KB113 reduces the need for surgery.
KB113 uses an HSV-1–based vector to deliver genes encoding interleukin-2 and interleukin-12 into tumors. It is designed to produce these immune-stimulating proteins locally and promote an immune response against cancer cells, potentially including those in lesions elsewhere on the body.
At the final assessment, 69 of 83 assessed lesions (83.1%) showed some degree of shrinkage, including 29 of 36 injected lesions and 40 of 47 non-injected lesions. More than 50% regression was observed in 42 of 83 lesions (50.6%). Investigators visually assessed selected lesions using a prespecified five-point clearance scale; these are lesion-level findings pooled across three patients, rather than patient response rates.
One injected lesion from each patient was biopsied after showing at least 90% clinical regression. All three selected biopsies showed no residual tumor. Krystal described the shrinkage of non-injected lesions as consistent with an abscopal effect, in which local treatment triggers an antitumor response at untreated sites.