FDA
New companion Dx approved for targeted prostate cancer therapy
Clinical takeaway: Patients with newly metastatic, hormone-sensitive prostate cancer can now be tested for PTEN protein loss to identify candidates for capivasertib plus abiraterone.
FDA approved the first immunohistochemistry test for PTEN protein loss in prostate adenocarcinoma, giving clinicians a way to identify a subgroup that standard hormone-sensitive therapy serves poorly. PTEN loss is common in prostate cancer and tracks with faster progression and reduced benefit from current standard of care.
The test, Roche's Ventana PTEN RxDx Assay, identifies patients eligible for capivasertib plus abiraterone, a regimen aimed directly at the consequences of that loss. About one in four metastatic hormone-sensitive cases typically qualify.
Metastatic hormone-sensitive prostate cancer is aggressive, with average survival of about five to six years after diagnosis. Until now, no treatment specifically targeted the PTEN-loss biology that marks the worst-responding cases. The approval rests on CAPItello-281, the phase 3 trial that used the assay to enroll patients with PTEN-deficient tumors; those who received capivasertib plus abiraterone had a statistically significant reduction in disease progression.
In the study, adding capivasertib to abiraterone produced a statistically significant and clinically meaningful reduction in radiographic disease progression in PTEN-deficient patients. The assay defines PTEN loss as no detectable protein in at least 90% of viable tumor cells, the same threshold used to enroll the trial.
The approval makes PTEN testing actionable at the point of a new metastatic diagnosis, turning a marker of poor prognosis into a route to a matched therapy. The practical question now is uptake: whether PTEN IHC gets built into the initial workup for hormone-sensitive disease, alongside the genomic testing many of these patients already receive.