A Phase I, Multi-Center, Dose Escalation Study of Atiprimod in Patients with Refractory or Relapsed Multiple Myeloma (MM).

Atiprimod (N-N-diethl-8, 8-dipropyl-2-azaspiro [4,5] decane-2-propanamine) is an orally bioavailable cationic amphilic compound that inhibited STAT 3 activation in MM cells. It effectively blocked the signaling pathway of interleukin-6, resulting in activation of caspase 3 and apoptosis (Amit-Vazina et al, Br J Cancer, 2005). Atiprimod has also induced cytotoxicity in dexamethasone, doxorubicin, and melphalan resistant MM cell lines (Hamasaki et al, Blood, 2005). Based on these encouraging in vitro data, we initiated a multi-center, phase I trial of atiprimod for patients (pts) with refractory or relapsed MM who had 2 prior lines of therapy and serum creatinine less than 2 mg/dl. Primary objectives were to evaluate the safety of atiprimod in MM pts and to identify the maximum tolerated dose (MTD). Each cycle of treatment consisted of 14 consecutive days of oral atiprimod followed by 14 consecutive days without treatment. A standard phase I dose escalation was used to determine MTD with atiprimod dose levels at 30 mg, 60 mg, 90 mg, 120 mg, and 180 mg. To date, 14 pts from 4 centers have been enrolled with evaluable data in 12 patients. Median age was 60 (range 44–64); median prior lines of therapy were 4 (range 3–7); median duration from initial treatment to registration to this trial was 36 months (range 19–76). Cohorts of 3 patients have been treated at 30, 60, 90,120 mg/day and 2 patients have been enrolled at the 180 mg/day level; no cohorts have been expanded because of dose-limiting toxicity. Median number of cycles received by MM pts was 2 (range 1–5). Common Grade 1 toxicity events included diarrhea, liver enzyme elevation and dyspepsia. There were two Grade 2 toxicity events with 1 neutropenia at the 90 mg/day level and 1 diarrhea at the 120 mg/day level. One pt had Grade 3 transaminase elevation (peak AST 402, ALT 469 units/L, bilirubin 0.5 mg/dl) during the second cycle that resolved on its own during the 14 day period off treatment. Two patients with rapidly rising serum M proteins prior to enrollment had a transient but clear reduction of their M proteins (30% and 80%) after the first 14 days of atiprimod. Two pts at higher dose levels noted subjective improvement in their bone pain. Atiprimod was generally well tolerated in this heavily treated group of MM pts. The MTD has not been reached. Although there has been no response to date, clinical activity is not expected until higher dose levels are evaluated (240 mg/day, 300 mg/day, and 360 mg/day). After the MTD has been established, the study of atiprimod combinations should be considered based on the in vitro assessment of synergy with other active agents.