Phase 2 Study of Dasatinib in Chinese Patients (Pts) with Chronic Myeloid Leukemia (CML) in Chronic Phase (CP) or Advanced Phase Who Are Resistant to or Intolerant of Imatinib (IM)

Abstract

Abstract 4434 Background:CML has a lower incidence in China than in Western countries and appears to affect a younger population (Au, Int J Hematol 2009). In recent years, IM has become the first-line standard of care across Asia for pts with newly diagnosed CML. In a cohort of Chinese pts, >25% of evaluable pts in CP failed to achieve a CCyR with first-line IM, and response rates were significantly lower in pts with accelerated-phase (AP) or blast-phase (BP) CML (Wang, J Exp Clin Cancer Res 2010). Dasatinib is a highly potent second-generation BCR-ABL inhibitor that has established efficacy and safety in pts with CML or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) after prior imatinib therapy. Dasatinib is approved by various regulatory authorities worldwide for first-line treatment of Philadelphia chromosome-positive (Ph+) CML in CP. Limited efficacy and safety data are available for second-generation BCR-ABL inhibitors in Chinese pts with CML or Ph+ ALL after imatinib therapy. Methods:In an open-label, single-arm phase 2 study, Chinese pts aged ≥18 years with IM resistant/intolerant CML or Ph+ ALL received dasatinib 100 mg once daily (CP) or 70 mg twice daily for AP/BP or Ph+ ALL. Bone marrow cytogenetic evaluation was performed at months 3 and 6, then every 6 months in CP pts, and was optional for pts with AP/BP or Ph+ ALL. Primary study objectives were to assess rates of major cytogenetic response (MCyR) in CP pts and complete and overall hematologic response (CHR and OHR) in pts with AP/BP or Ph+ ALL. OHR was defined as CHR, no evidence of leukemia, or return to CP. Treatment continued until disease progression or intolerable toxicity. Results:Of 140 enrolled pts, 121 pts had received ≥1 dose of dasatinib and were evaluable (59 with CP, 25 with AP, 35 with BP, and 2 with Ph+ ALL). Of pts with CML-CP or AP/BP/Ph+ ALL, 52 (88%) and 53 (85%) were IM resistant, 4 (7%) and 5 (8%) were IM intolerant, and 3 (5%) and 4 (6%) were both IM resistant and intolerant. Median time from original CML diagnosis to first dasatinib dose was 46.3 months (CP) and 50.2 months (AP/BP/Ph+ ALL). More than half of pts had received prior interferon therapy. At last follow-up, dasatinib therapy had been discontinued by 7 pts (12%) with CP and 43 pts (69%) with AP/BP/Ph+ ALL, due to disease progression or loss of response in 2% and 35%, study drug toxicity in 2% and 11%, stem-cell transplant in 0% and 5%, death in 2% and 2%, and other reasons in 7% and 16%, respectively. After a minimum of 12 months follow-up, MCyR was achieved by 30 pts with CP (51%), 10 pts with AP (40%), and 8 pts with BP/Ph+ ALL (22%). In pts with CP, median time to MCyR was 12 weeks and no patient lost MCyR. Complete cytogenetic response was achieved by 25 pts with CP (44%), 7 pts with AP (28%), and 6 pts with BP/Ph+ ALL (16%). CHR was achieved by 54 pts with CP (92%), 13 pts with AP (52%), and 6 pts (16%) with BP/Ph+ ALL. In CP pts, most (51/54) who achieved CHR did so within 2 months. Median times to CHR were 16 and 12 weeks for pts with AP and BP/Ph+ ALL, respectively. After 12 months, 3 pts in CP, 2 pts in AP, and 1 pt in BP had lost their CHR. OHR was achieved by 23 and 13 pts (92% and 35%) with AP and BP/Ph+ ALL, respectively. In safety assessments (Table), grade 3/4 cytopenia was frequent but managed by dose interruption/reduction or supportive care, with 1 pt discontinued for cytopenia. Pleural effusion of any grade occurred in 15%, 20%, and 22% of pts with CP, AP, and BP/Ph+ ALL, respectively. Grade 3/4 pleural effusion occurred in 1 pt with CML-CP (2%) and 5 pts with AP/BP/Ph+ ALL (8%). Conclusions:The current study confirms the efficacy and safety of dasatinib in Chinese pts with CML or Ph+ ALL that is resistant or intolerant to IM. Results were consistent with data from global trial populations.Table:Drug-related nonhematologic AEs and hematologic AEs by disease stagePatients, n (%)CP (n=59)AP (n=25)BP/Ph+ ALL (n=37)Nonhematologic AEsAny grade31 (53)18 (72)30 (81)Grade 3/47 (12)12 (48)21 (57)AE types (any grade, ≥10% of any disease group)Pleural effusion9 (15)5 (20)8 (22)Lung infection1 (2)4 (16)5 (14)Pneumonia0 (0)3 (12)1 (3)Headache12 (20)3 (12)1 (3)Diarrhea4 (7)5 (20)3 (8)Pyrexia1 (2)2 (8)7 (19)Grade 3/4 hematologic AEsNeutropenia31 (53)22 (88)29 (78)Thrombocytopenia36 (61)20 (80)33 (89) Disclosures:No relevant conflicts of interest to declare.