At the 2023 American Society of Clinical Oncology (ASCO) annual meeting in Chicago, Illinois, Jennifer Ann Woyach, MD, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio, shared data on ibrutinib combined with obinutuzumab and venetoclax vs ibrutinib plus obinutuzumab for the frontline treatment of older patients with chronic lymphocytic leukemia (CLL) in the setting of the COVID-19 pandemic.

The data came from the randomized phase 3 study A041702. 

What was the rationale for the phase 3 A041702 study on frontline treatment regimens for older patients with CLL?

This is actually the successor study to the previous trial, A041202, which demonstrated that the BTK inhibitor ibrutinib, either alone or in combination with rituximab, produced superior progression-free survival to the chemoimmunotherapy regimen of bendamustine plus rituximab. So, although ibrutinib can produce durable remissions in this patient population, it has to be given indefinitely, which can increase the risk for long-term toxicity, as well as increase financial pressure on the patient.

The purpose of this study was to see whether we could add the BCL-2 inhibitor venetoclax to the backbone of ibrutinib plus obinutuzumab in an attempt to produce more complete responses with undetectable minimal residual disease, thus allowing a successful therapy discontinuation. Patients enrolled in the study had to be age 70 or older initially, and then the study was later amended to include patients age 65 and older. But the median age [of] study patients was 74.

How was this study conducted?

Patients were randomized in a 1-to-1 fashion to either ibrutinib plus obinutuzumab, or IO, or the triplet of ibrutinib, venetoclax, obinutuzumab, or IVO. All patients in both arms had obinutuzumab treatment for 6 months, and then the rest of their treatment continued for a year. And then all patients underwent a response evaluation at the end of 14 cycles with CAT scans, exam, and a bone marrow biopsy. 

In the doublet arm, the IO arm, patients would then all continue ibrutinib indefinitely. In the triplet IVO arm, patients underwent a response-adapted discontinuation, where patients who had an undetectable minimal residual disease (MRD) complete response (CR) went off of all treatment, and all other patients continued ibrutinib indefinitely.

What were the results? 

The study is being presented now because it did cross its futility boundary, demonstrating that IVO is not superior to IO in this patient population. However, the study unfortunately was very impacted by COVID-19, and we actually had a number of patients in both arms die of COVID, and unfortunately, more patients in the IVO arm died of COVID compared to the IO arm. So, 19 patients in the IVO arm died of COVID, compared to 11 in the IO arm.

When we look at the study results with a median follow-up of about 14 months, the PFS [progression-free survival] curves are fairly similar. The trend, however, does favor ibrutinib-obinutuzumab. When we censored patients who died of COVID, the 2 arms, again remained similar in terms of PFS, but actually the trend then favors the IVO arm. When we look at toxicity outside of COVID-19, it is fairly similar between the 2 arms. Non-hematologic toxicity, in general, was identical between IVO and IO. Hematologic toxicity was a little bit higher in IVO compared with IO.

What conclusions can be drawn from this study? What are the next steps for investigating these treatment regimens in this or other patient populations? 

Because of the discrepancy in death between the 2 arms, we think it's going to be really important to follow this study long-term. Even though we're not going to see a PFS advantage for IVO versus IO, long-term follow-up will be important to the determine whether there are any patients who benefit from the addition of venetoclax and potentially therapy discontinuation.

Source:

Woyach J A, Yin J, Brown J R, et al. Results of a phase 3 study of IVO vs IO for previously untreated older patients (pts) with chronic lymphocytic leukemia (CLL) and impact of COVID-19 (Alliance). Presented at ASCO Annual Meeting; June 2-6, 2023; Chicago, IL. Abstract 7500.