Tolerability and Efficacy of Crenolanib and Cytarabine/Anthracycline Chemotherapy in Older Patients (Aged 61 to 75) with Newly Diagnosed FLT3-Mutated Acute Myeloid Leukemia (AML)
Authors: Wang Eunice S. , Griffiths Elizabeth A. , Walter Roland B. , Tallman Martin S. , Goldberg Aaron D , Messahel Boo , Stone Richard M. 
Published: November 2019

Background: Older AML patients often present with comorbidities and may have a compromised ability to tolerate intensive chemotherapy. These patients are more likely to have AML secondary to MDS/MPN and are considered to have a biologically distinct disease compared to their younger counterparts, with more frequent occurrence of adverse-risk cytogenetic abnormalities and mutations in genes regulating epigenetic modifications. In addition, the heterogeneity of driver mutations within a single patient contributes to limited responses to standard induction chemotherapy. While FLT3 mutations occur in this population, they are often subclonal, adding to the challenge of eradicating AML in older adult patients. Studies combining sorafenib or midostaurin with standard induction chemotherapy have shown relatively modest improvements in response rates and survival, and relapses, both early and late, remain a major concern.

There is a major unmet need for optimizing chemotherapy and TKI treatment in this medically fragile population. We here report the safety and efficacy results in newly diagnosed older patients with FLT3 mutant AML treated with crenolanib, a type I FLT3 inhibitor, in combination with intensive induction and consolidation chemotherapy (NCT02283177).

Methods: Fifteen consecutively treated patients, aged 61-75 (median age: 68), at four academic cancer centers were included in this analysis. Patients received 7+3 induction with cytarabine 100 mg/m2 for 7 days and either daunorubicin 60 mg/m2 or idarubicin 12 mg/m2 for 3 days. Crenolanib 100 mg TID was administered continuously starting 24 hours after chemotherapy until 72 hours prior to the next chemotherapy cycle. Consolidation consisted of up to 4 cycles of high-dose cytarabine (HiDAC: 1 g/m2) q12h on days 1, 3, and 5 with crenolanib starting 24 hours after the final HiDAC dose. Eligible patients proceeded to allogeneic hematopoietic stem cell transplant (HSCT). Maintenance with crenolanib at 100mg TID was started after HiDAC or 30-90 days after HSCT for up to 12 cycles.

Results: Fourteen patients completed induction chemotherapy (one patient withdrew consent at day 19). Crenolanib could be safely combined with either daunorubicin or idarubicin based induction chemotherapy. The most common adverse events (grade ≥3) were diarrhea, nausea, and febrile neutropenia. Ten of 14 patients were able to receive full doses of crenolanib during induction. The major reason for dose reduction was edema in 3 patients and GI bleeding in 1 patient. There was one treatment-related death, with 93% survival at 30 and 60 days and 87% survival at 100 days.

Complete remissions with full count recovery (CR) were achieved in 10 of 15 patients after just one cycle of induction chemotherapy. Two patients achieved a complete remission after reinduction for an overall CR rate of 86%. Of the 12 patients who achieved CR, 10 patients received HiDAC consolidation, with two patients unable to receive consolidation therapy on study. Three patients received crenolanib maintenance after multiple cycles of HiDAC consolidation. Six patients underwent HSCT and 3 received crenolanib maintenance.

As of July 2019, median OS for the intent to treat population is 20.2 months. One-year survival was 67% and 5 patients remain alive and in remission. All 5 long term survivors were ≤70 years old. All surviving patients received either multiple cycles of HiDAC or HiDAC plus transplant, and 4/5 underwent crenolanib maintenance. The patient who did not receive transplant completed 3 cycles of HiDAC consolidation and a full year of crenolanib maintenance.

Summary/Conclusion: This safety study shows that crenolanib can be combined at full doses (100mg TID) for the duration of 7+3 induction, consolidation, and maintenance in older patients with FLT3 mutant AML. Therapy was relatively well tolerated, with less than one third of patients requiring dose reductions. Long-term survival rates are encouraging in this high-risk population, but additional studies are needed to confirm the efficacy of this combination older adults.

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Disclosures

Wang: Pfizer: Other: Advisory role, Speakers Bureau; Stemline: Other: Advisory role, Speakers Bureau; Abbvie: Other: Advisory role; Kite: Other: Advisory role; Jazz: Other: Advisory role; Astellas: Other: Advisory role, Speakers Bureau; celyad: Other: Advisory role; Daiichi: Other: Advisory role; Amgen: Other: Advisory role; Agios: Other: Advisory role. Griffiths:Abbvie, Inc.: Consultancy; Genentech, Inc.: Research Funding; Celgene, Inc: Consultancy, Research Funding; Onconova Therapeutics: Other: PI on a clinical trial; Novartis Inc.: Consultancy; Appelis Pharmaceuticals: Other: PI on a clinical trial; Onconova Therapeutics: Other: PI on a clinical trial; Appelis Pharmaceuticals: Other: PI on a clinical trial; New Link Genetics: Consultancy; Partner Therapeutics: Consultancy; Genentech, Inc.: Research Funding; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Abbvie, Inc.: Consultancy, PI on a clinical trial; Celgene, Inc: Consultancy, Research Funding; Boston Scientific: Consultancy; Boston Scientific: Consultancy; Persimmune: Consultancy; Persimmune: Consultancy; New Link Genetics: Consultancy; Partner Therapeutics: Consultancy; Novartis Inc.: Consultancy. Walter:Jazz Pharmaceuticals: Consultancy; Agios: Consultancy; Amgen: Consultancy; Amphivena Therapeutics: Consultancy, Equity Ownership; Aptevo Therapeutics: Consultancy, Research Funding; Argenx BVBA: Consultancy; Astellas: Consultancy; BioLineRx: Consultancy; Kite Pharma: Consultancy; New Link Genetics: Consultancy; Pfizer: Consultancy, Research Funding; Race Oncology: Consultancy; Seattle Genetics: Research Funding; Boston Biomedical: Consultancy; Covagen: Consultancy; BiVictriX: Consultancy; Daiichi Sankyo: Consultancy; Boehringer Ingelheim: Consultancy. Tallman:Hematology Oncology of Indiana: Honoraria; Salzberg Weill Cornall MSKCC Seminar in Hematologic Malignancies: Honoraria; University of Oklahoma Medical Center: Honoraria; Bioline: Membership on an entity's Board of Directors or advisory committees, Research Funding; BioSight: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Nohla: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rigel: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics: Research Funding; Arog Pharmaceuticals: Research Funding; Cellerant Therapeutics: Research Funding; Orsenix: Membership on an entity's Board of Directors or advisory committees, Research Funding; UpToDate: Patents & Royalties; Mayo Clinic: Honoraria; New Orleans Summer Cancer Conference: Honoraria; Indy Hematology Review: Honoraria; Amgen: Consultancy; 14th Annual Miami Cancer Meeting: Honoraria; Danbury Hospital Tumor Board: Honoraria; International Conference in Leukemia: Honoraria. Goldberg:ADC Therapeutics: Research Funding; Arog Pharmaceuticals: Research Funding; American Society of Clinical Oncology: Research Funding; American Society of Hematology: Research Funding; Celgene: Consultancy; Abbvie: Research Funding; Pfizer: Research Funding; Abbvie: Consultancy; Daiichi-Sankyo: Consultancy, Research Funding; DAVA Oncology: Honoraria. Messahel:Arog Pharmaceuticals: Employment. Stone:Pfizer: Consultancy; Stemline: Consultancy; Astra-Zeneca: Consultancy; Argenix: Other: DSMB; Otsuka: Consultancy; Astellas: Consultancy; Argenix: Other: DSMB; Celgene: Consultancy, Other: DSMB; Stemline: Consultancy; Actinium: Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy; Biolinerx: Consultancy; Biosight: Consultancy; Trovagene: Consultancy; Arog: Consultancy, Research Funding; Takeda: Other: DSMB; Novartis: Consultancy, Research Funding; Daiichi-Sankyo: Consultancy; Celgene: Consultancy, Other: DSMB; Abbvie: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Takeda: Other: DSMB; Biolinerx: Consultancy; Daiichi-Sankyo: Consultancy; Actinium: Membership on an entity's Board of Directors or advisory committees; Otsuka: Consultancy; Jazz: Consultancy; Trovagene: Consultancy; Astra-Zeneca: Consultancy; Novartis: Consultancy, Research Funding; Roche: Consultancy; Macrogenics: Consultancy; Agios: Consultancy, Research Funding; Biosight: Consultancy; Abbvie: Consultancy, Research Funding; Arog: Consultancy, Research Funding; Pfizer: Consultancy; Trovagene: Consultancy; Novartis: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Arog: Consultancy, Research Funding; Macrogenics: Consultancy; Otsuka: Consultancy; Argenix: Other: DSMB; Astellas: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy; Biolinerx: Consultancy.