Acalabrutinib Combo Promising as Frontline Treatment for CLL

SAN DIEGO — Treatment with the oral Bruton’s tyrosine kinase (BTK) inhibitor acalabrutinib in combination with venetoclax was associated with improved progression-free survival compared with standard-of-care chemoimmunotherapy in frontline treatment of chronic lymphocytic leukemia (CLL), according to a prespecified interim analysis of the AMPLIFY trial.

In fit, adult patients without del(17p) or TP53 mutations, the acalabrutinib-venetoclax combination, with or without obinutuzumab, demonstrated a statistically significant and clinically meaningful improvement in progression-free survival compared with a combination of fludarabine-cyclophosphamide-rituximab or bendamustine-rituximab, reported principal investigator Jennifer R. Brown, MD, PhD,who presented the results at the American Society of Hematology (ASH) 2024 Annual Meeting.

Patients with CLL have several frontline treatment options, which include chemoimmunotherapy for low-risk disease as well as venetoclax plus the first-generation BTK inhibitor ibrutinib.

While fixed-duration venetoclax plus ibrutinib can result in deep, durable responses, cardiac toxicity remains a concern, particularly in older patients, explained Brown, director of the CLL Center of the Division of Hematologic Malignancies, Dana-Farber Cancer Institute, Boston, during a press conference.

Acalabrutinib is a highly selective second-generation BTK inhibitor with improved safety and tolerability compared with ibrutinib. Brown and colleagues wanted to see whether this second-generation BTK inhibitor alongside venetoclax provided a clinical benefit and fewer cardiac toxicities as a frontline option in this patient population.

“AMPLIFY provides the first phase 3 evidence of fixed-duration therapy with a combination of venetoclax and a second-generation BTK inhibitor in patients with treatment-naive CLL,” Brown said. And these results “show the promise of a new all-oral fixed-duration therapy approach, which would allow patients to take breaks from treatment, reducing the risk of long-term adverse events and drug resistance,” Brown, also from Harvard Medical School, Boston, added in a press release.

Study Details

AMPLIFY randomized 867 patients (median age, 61 years) to three treatment arms: Acalabrutinib in combination with venetoclax alone (n = 291), acalabrutinib and venetoclax with obinutuzumab (n = 286), or the investigator’s choice of chemoimmunotherapy — a combination of fludarabine-cyclophosphamide-rituximab or bendamustine-rituximab (n = 290). The median follow-up was 41 months.

Compared with 66.5% in the chemoimmunotherapy arm, 83.1% of patients in the acalabrutinib-venetoclax arm and 76.5% of the acalabrutinib-venetoclax-obinutuzumab arm reached the primary endpoint of 36-month progression-free survival (hazard ratios [HRs] of 0.65 and 0.42, respectively). Median progression-free survival was not reached in the two acalabrutinib arms, compared with 47.6 months in the chemotherapy arm.

More than half of all participants (58.6%) had unmutated immunoglobulin heavy-chain variable region gene (IGHV) status. In a subgroup analysis, patients on either acalabrutinib regimen experienced a significant improvement in progression-free survival compared with those on chemoimmunotherapy, regardless of IGHV status.

It was “particularly noticeable” in the acalabrutinib-venetoclax-obinutuzumab arm (HR, 0.35) that patients with unmutated IGHV were doing as well as those with mutated IGHV, “suggesting that the addition of obinutuzumab may overcome the adverse impact of unmutated IGHV,” Brown said.

Patients also demonstrated a robust response in both investigational arms with an overall response rate of 92.8% for acalabrutinib-venetoclax and 92.7% for acalabrutinib-venetoclax-obinutuzumab compared with 75.2% for chemoimmunotherapy (P 

In addition, compared with chemoimmunotherapy, acalabrutinib-venetoclax was associated with a significant improvement in overall survival (HR, 0.33; 95% CI, 0.18-0.56). Acalabrutinib-venetoclax-obinutuzumab was associated with better overall survival (HR, 0.78), but the findings were not statistically significant.

When considering COVID-19 deaths, overall survival findings were significant for both acalabrutinib regimens, Brown reported.

COVID-19 deaths were observed in 10 patients in the acalabrutinib-venetoclax arm, 25 in the acalabrutinib-venetoclax-obinutuzumab arm, and 21 in the chemoimmunotherapy arm.

In terms of safety, both acalabrutinib treatment regimens demonstrated “tolerable safety profiles with a low incidence of cardiac adverse events typically associated with BTK inhibitors, including atrial fibrillation or hypertension,” she reported.

Any serious adverse events were observed in 24.7% of the acalabrutinib-venetoclax patients, 38.4% of those receiving acalabrutinib-venetoclax-obinutuzumab, and 27.4% on chemoimmunotherapy. Serious adverse events leading to death occurred in 3.4%, 6.0%, and 3.5% of patients in the three groups, respectively, and adverse events leading to death occurred in about 8%, 20%, and 10.8%, respectively, of patients.

The most common adverse event was neutropenia, with grade 3 or higher neutropenia occurring in 32.3% of patients in the acalabrutinib-venetoclax arm and 46.1% in the acalabrutinib-venetoclax-obinutuzumab group, compared with 43.2% of patients with chemoimmunotherapy.

As for cardiac events, 9.3% of patients in the acalabrutinib-venetoclax group experienced an event of any grade compared with 12% in the acalabrutinib-venetoclax-obinutuzumab group and 3.5% in the chemoimmunotherapy group.

To Add or Not to Add Obinutuzumab

Asked how clinicians might decide between the two acalabrutinib regimens, Brown said, “If you add the obinutuzumab, it does add more work for the patient,” and it adds more toxicity.

But, she noted, it might optimize progression-free survival.

“I think when physicians are considering whether to use the two- or the three-drug regimen, they have to take account of the patient in front of them,” Brown said. “The acalabrutinib-venetoclax regimen is a very well-tolerated oral regimen, which is really going to be suitable for anyone, and I think, easy to use in the community.”

The fact that there were more COVID-19 deaths in the obinutuzumab arm compared with the acalabrutinib-venetoclax arm suggests more immunosuppression in the three-drug regimen, said session moderator Deborah M. Stephens, DO, associate professor of medicine and director of the Chronic Lymphocytic Leukemia and Richter’s Program at the University of North Carolina School of Medicine in Chapel Hill, North Carolina.

This finding could “call into question whether acalabrutinib-venetoclax may have a better risk/benefit ratio when compared to acalabrutinib-venetoclax-obinutuzumab,” she wrote in an email to Medscape Medical News.

Overall, “AMPLIFY is an important trial, and these data will likely be submitted to the US FDA and regulatory bodies of other involved countries to gain approval of the acalabrutinib + venetoclax +/− obinutuzumab regimen,” Stephens added.

“Notably, this is another in a string of phase 3 trials showing that survival is prolonged with targeted agents compared to chemoimmunotherapy,” indicating that standard chemoimmunotherapy “should be considered obsolete as a control arm for phase 3 studies in the frontline treatment of CLL,” said Stephens.

Alexey Danilov, MD, PhD, another CLL specialist from City of Hope, Duarte, California, who was also presenting at the press conference, said, “I don’t see a full justification to use the acalabrutinib-venetoclax-obinutuzumab regimen across the board in all patients, even though progression-free is better. I do think that, unfortunately, this benefit is offset by increased frequency of adverse events.”

Although it looks like “the majority of patients will be very good candidates for acalabrutinib-venetoclax, with impressive progression-free survival, I think we will still have to define who these patients are,” he added.

However, overall, he was enthusiastic. “This is anticipated to get approval as the first oral doublet front line therapy of CLL, and I think many patients do — in my clinic at least — prefer the idea of finite duration therapy to continuous BTK inhibitors.”

The study was funded by AstraZeneca. Brown disclosed the following: Consultancy with Acerta/AstraZeneca, Genentech/Roche, AbbVie, and multiple other companies. Danilov disclosed the following: Consultancy with AstraZeneca, Genentech, AbbVie, among others. Stephens had no relevant disclosures.

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.