CLL Research: Acalabrutinib Triple Combination in Chronic Lymphocytic Leukemia (CLL)
During the 62nd Annual Meeting and Exposition of the American Society of Hematology (ASH2020), Dr. Jennifer A Woyach, MD, a chronic lymphocytic leukemia specialist at the James Cancer Center of the Ohio State University in Columbus, Ohio, gave an oral poster presentation entitled Acalabrutinib in Combination with Venetoclax and Obinutuzumab or Rituximab in Patients with Treatment-Naïve or Relapsed/Refractory Chronic Lymphocytic Leukemia.
Background: Acalabrutinib Triple Combination - ACE-CL-003 Study
Acalabrutinib is a second-generation, highly selective, covalent Bruton’s Tyrosine Kinase (BTK) inhibitor approved for marketing under the tradename Calquence® in multiple countries. Responses to acalabrutinib monotherapy are durable in CLL. Still, patients must remain on this drug indefinitely until either their disease progresses (usually due to their CLL cells becoming resistant to acalabrutinib) or the side effects become unmanageable. Only a small percentage of patients achieve a complete response (CR) with acalabrutinib alone.
Researchers theorize that using acalabrutinib combined with other agents may increase the depth of response, leading to a higher percentage of CRs and undetectable Minimal Residual Disease (uMRD) or negative MRD. Experience has shown that patients who achieve more profound responses have more prolonged progression-free survival (PFS) and overall survival (OS).
Previously, researchers studied the two-drug combination of acalabrutinib and obinutuzumab (Gazyva®) in the ACE-CL-003 Phase 1b trial in treatment naïve patients (TN) and relapsed or refractory (RR) patients. In the two cohorts, TN and RR, the median follow-up was 3.5 years and showed that the two-drug combination was well tolerated and produced durable responses. Five of 19 TN patients (26%) and four of 26 RR patients (15%) reached MRD negativity in the bone marrow at twelve months. MRD responses measured in the blood deepened over time. TN patients, in general, displayed more profound MRD negativity than RR patients.
In the earlier ELEVATE-TN Phase 3 study, acalabrutinib with obinutuzumab significantly improved PFS over chemoimmunotherapy.
This report covers two cohorts that received triple-combination therapy. RR patients received acalabrutinib + venetoclax and rituximab, an anti-CD20 monoclonal antibody (MAB). In the TN cohort, patients received acalabrutinib + venetoclax and obinutuzumab, a newer anti-CD20 MAB. You might ask, “why to study different monoclonal antibodies?” The reason is simple: venetoclax + rituximab is an approved combination for RR CLL, and venetoclax + obinutuzumab is a supported combination for TN within the National Comprehensive Cancer Network (NCCN) guidelines.
Methods: Acalabrutinib + Venetoclax + Anti-CD20 Monoclonal Antibody
To qualify for this trial, patients had to be at least 18 years of age; however, the RR group’s median age was 66.5 (range, 55-72), and the TN cohort was 60.5 (range, 42-73.) Further, patients have an Eastern Cooperative Oncology Group (ECOG) performance score of less than two. Patients with an ECOG score are of zero are completely ambulatory and have no restrictions on their activities and ability to perform strenuous work. Those with a score of one cannot perform strenuous work but are fully mobile and able to perform light work.
Within the RR group, patients who had received prior treatment with a BTK inhibitor such as ibrutinib or acalabrutinib were permitted in this trial as long as they had not experienced disease progression.
Results: Acalabrutinib Triple Combination - ACE-CL-003 Study
The median number of treatment cycles in RR patients was 29 (range, 15-30) for acalabrutinib and 13 (range 10-14) for venetoclax. All RR patients received all six scheduled doses of rituximab. In the TN cohort, the median number of cycles of acalabrutinib was 28 (range, 18-29) and 13 (range, 13.0-14) for venetoclax. All TN patients received all six scheduled doses of obinutuzumab.
The reasons for discontinuing therapy were adverse events (AEs) in one patient in each group (RR: grade 1 purpura {blood spots or skin hemorrhages}, and TN: grade 2 head discomfort.)
Reported adverse events were similar to the side-effect profiles of the individual agents. Seven RR patients (58%) and four TN patients (33%) had cardiac adverse events. Of these cardiac AEs, only one (8%) was a Grade 3 atrial fibrillation (AF) in a patient with a prior history of AF. For more information on cardiac toxicities associated with acalabrutinib, see our recent coverage of an ASH2020 poster presentation by Dr. Jennifer Brown, the head of the CLL program at Dana-Farber Cancer Institute.
Conclusions
Acalabrutinib Triple Combination therapy with acalabrutinib + venetoclax and an anti-CD20 antibody leads to a tolerable safety profile with high CR and uMRD rates in both RR and TN CLL patients, with minimal to no drug-drug interactions.
A similar three-drug combination with ibrutinib is also underway.
I participated in the phase 3 trial of acalabrutinib at the NIH from June 2016 until I became resistant in June 2018, then has Venclexta / Rituxan therapy for 13 / 6 months from August 2018 through Sept 2019. Although I had digestive system issues ( diarrhea, gas ) I tolerated it and became MRD -. I have been drug free and in remission 18 months and loving life!
That’s awesome news that you reached undetectable MRD. I joined that club last October after adding venetoclax to the ibrutinib I was already taking and still take after I could stop the venetoclax. I agreed with my specialist to stay on the ibrutinib because I’m deletions 17p and 11q, and I’m unmutated, so high-risk profile.
I couldn’t tolerate the many side effects I received from Ibrutinib so switched to Alacabrutinib I have bright CD 20 T12 mutated so a CD 20 should work well for me. I look forward to drug free life.