Eric L. Smith, MD, PhD
Using combination regimens in an effective manner will likely be a go-to method with immunotherapy in multiple myeloma, in an effort to induce durable responses in patients. This was the message by the Eric L. Smith, MD, PhD, in a presentation at the 34th Annual Chemotherapy Foundation Symposium™.
“In combinations we really do see dramatic increases in efficacy, when lenalidomide and dexamethasone are used in the combinations,” said Smith, a medical oncologist at Memorial Sloan Kettering Cancer Center. “The monotherapy results are somewhat less exciting. Combination therapies are really going to be the key here.”
As single agents, many of the immunotherapies have demonstrated lackluster findings for patients with relapsed multiple myeloma. In these studies, the anti–SLAMF7 agent elotuzumab (Empliciti) failed to elicit responses, though the stable disease rate was 26.5%. Monotherapy with the CD38 antibody daratumumab (Darzalex) fared slightly better, Smith noted, with a single-agent response rate of 36%, which included complete remissions (CRs).
When looking at these antibodies in combination, the results were far more substantial. In the phase III ELOQUENT-2 study, the combination of elotuzumab, lenalidomide (Revlimid), and dexamethasone elicited an objective response rate (ORR) of 78.5% and a median progression-free survival (PFS) of 19.4 months. Similarly, in the phase III POLLUX trial exploring daratumumab, lenalidomide, and dexamethasone, the ORR was 92.9%, and the 12-month PFS was 83.2%.
Further immunotherapeutic potential has been realized across various types of cancer through the inhibition of various checkpoints, such as PD-1 and CTLA-4. To this end, monotherapy with the PD-1 inhibitor nivolumab (Opdivo) was explored across hematologic malignancies. Unfortunately, only 1 of 27 patients with myeloma responded to the single agent. In a separate experience using pembrolizumab (Keytruda), the combination of the PD-1 inhibitor with lenalidomide and dexamethasone reduced M protein levels in 88% of patients with myeloma. The ORR in this relapsed/refractory population was 50%, which included 1 CR.
“Even in a lenalidomide-refractory population, we still see really impressive overall response rates, again, going back to the fact that combination therapies are really working to have the T cells overcome the immune suppression of the myeloma cell microenvironment,” said Smith.
In addition to monoclonal antibodies and checkpoint inhibitors, cellular therapies, such as chimeric antigen receptor (CAR)-modified T cell therapies, are also under exploration. This approach builds upon years of experience with allogeneic stem cell transplantation, said Smith.
To date, the main concerns with this approach have been cytokine release syndrome and neurotoxicity. Treatment algorithms are being put into place to counter these adverse events, primarily the use of IL-6 antibodies, Smith noted. Additionally, the construct of these therapies are evolving to help ameliorate these events.
“The CAR T cell therapy field is advancing. We're now putting in not only 1 or 2 genes but 3 genes into the cell, that include ways to modify the microenvironment or to secrete cytokines or to express other ligands that might give the cells an advantage,” said Smith.
The CAR T cell therapies have been explored in myeloma with intriguing, yet limited, results. These early studies have utilized CAR T cell therapies directed against CD19, which is not heavily expressed in myeloma. As a result, a new target needed to be identified, noted Smith. In the past year, a new target, B-cell maturation antigen (BCMA), has moved to the forefront of development for its myeloma-specific activity.
In a small study, a BCMA-targeted CAR T cell therapy was explored in 12 patients with myeloma following cyclophosphamide and fludarabine preconditioning. Overall, there was 1 stringent CR that lasted for 17 weeks and 1 very good partial response that was still ongoing at 26 weeks. More results from this approach are expected in the next 12 months.