Second interim analysis (IA2) results from a phase II trial of TAK-385, an oral GnRH antagonist, in prostate cancer patients (pts).

200 Background: Gonadotropin-releasing hormone (GnRH) antagonists achieve rapid decrease in testosterone (T) without transient T surge seen with GnRH agonists and thus may avoid clinical flare symptomatology. TAK-385 is an investigational, oral, non-peptide GnRH antagonist highly selective for the human GnRH receptor (IC 50 0.12 nM). We report IA2 results from a phase 2, randomized, open label, parallel group study of TAK-385 in pts with advanced prostate cancer (NCT02083185). Methods: Pts aged ≥ 18 yrs with histologically confirmed prostate cancer, baseline T > 150 ng/dL and prostate-specific antigen (PSA) > 2 ng/mL, who were candidates for first-line androgen deprivation therapy, were randomized to receive oral TAK-385, 80 or 120 mg, once daily (QD) or leuprorelin (LEU) 22.5 mg subcutaneously every 12 wks, for 48 wks. The primary endpoint was effective castration rate of TAK-385 (T < 50 ng/dL) from wk 5–24. Secondary endpoints included: safety, pharmacokinetics (PK), and PSA. Results: At data cut-off, 75 pts had received TAK-385 (39 at 80 mg, 36 at 120 mg QD); 20 pts received LEU. Median age was 73 yrs with TAK-385 and 68.5 yrs with LEU; median treatment duration was 35.1 wks and 37.8 wks. After 3 days/4 wks/24 wks of treatment, median T was 36.9/10.6/8.9 ng/dL with TAK385 vs 648.1/13.0/11.5 ng/dL with LEU. T < 50 ng/dL was sustained over 5–24 wks in 92% vs 95% of pts (TAK-385 vs LEU). After 24 wks, PSA was reduced by 97.3% to a median of 0.1 ng/mL with TAK-385 vs 92.4% to 0.2 ng/mL with LEU. All-grade adverse events occurred in 91% vs 95% of pts (TAK-385 vs LEU); the most common were hot flush (59/60%), fatigue (21/15%), elevated alanine aminotransferase (9/10%), nasopharyngitis (8/5%), and elevated aspartate aminotransferase (5/10%). Initial analysis of pooled phase 1/2 data showed similar PK in the phase 2 pts and in previously studied healthy men, with dose-proportional plasma trough levels over > 6 mos. Conclusions: At IA2, the efficacy of TAK-385 was consistent with the GnRH antagonist mechanism of action and the safety profile was good. TAK-385 rapidly reduced T and sustained castration ( < 50 ng/dL) over 24 wks. Further investigation of TAK-385, as an option to injectable GnRH therapies, is warranted. Clinical trial information: NCT02083185.

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