Phase 2 Study of Oblimersen Sodium (G3139; Bcl-2 Antisense; Genasense®) Plus Gemtuzumab Ozogamcin (Mylotarg®) in Elderly Patients with Relapsed Acute Myeloid Leukemia (AML).

Patients with relapsed AML over the age of 60 have a poor prognosis. Gemtuzumab ozogamicin (GO) has been approved for older pts in first relapse, although many pts who attain complete remission (CR) do not fully recover normal platelet count (so-called CRp). In vitro studies have shown that oblimersen down-regulates Bcl-2 in AML cells and enhances apoptotic cell death induced by GO. We conducted a Phase 2 study to evaluate the safety and efficacy of GO combined with oblimersen for older pts with AML. Eligibility requirements included: age ≥ 60 yrs; AML in 1^st relapse; ≥ 3 mos 1^st CR duration; ≥ 25% CD33-positive AML cells. Pts received oblimersen at a dose of 7 mg/kg/d for 7 days by CIV beginning on days 1 and 15; GO was given at a dose of 9 mg/m² IV over 2 hrs on days 4 and 18. A total of 48 pts were enrolled (ITT population), all of whom received at least 1 dose of oblimersen; 9 pts failed to receive the required 2 doses of GO (per-protocol population, n=39). The median age was 67 (range, 59 to 88 yrs). Duration of 1^st CR: < 6 mos: 7 pts; (15%); 6 to 12 mos: 29 pts (60%); > 12 mos: 12 pts (25%). No. of prior regimens: 1 (17 pts, 35%); 2 or 3 (26 pts, 54%); ≥ 4 (5 pts, 10%). Among treated pts, 79% completed 21 days of protocol therapy. Overall, 12 pts achieved a major response, either CR (n=5) or CRp (n=7), for an ITT response rate of 25% and a per-protocol response rate of 31%. The median time to remission was 52 days. Ten of the 12 responders survived > 6 mos, whereas only 6 non-responders survived ≥ 6 mos. Serious adverse events for the oblimersen/GO combination were qualitatively similar to those reported for GO alone and included among other reactions: Grade 3-4 febrile neutropenia (42%) or thrombocytopenia 33%; nausea; fever; rigors, and dyspnea. Treatment-emergent adverse reactions led to discontinuation of protocol therapy in 10 pts (21%). The most common serious adverse event was febrile neutropenia (25%). One pt (2.1%) died during treatment (sepsis) and 16 pts (33%) died within 30 days of last study medication (infection, bleeding, respiratory failure, progressive AML, and other disease-related complications). No episodes of VOD were observed. Oblimersen can be safely combined with GO; however, pts enrolled in this study appear to have had more unfavorable characteristics at entry compared with prior studies using GO alone in pts with relapsed AML. Therefore, assessment of an incremental benefit from the addition of oblimersen will require a randomized trial.