SUMMARY: Multiple Myeloma is a clonal disorder of plasma cells in the bone marrow and the American Cancer Society estimates that in the United States, 35,730 new cases will be diagnosed in 2023 and 12,590 patients will die of the disease. Multiple Myeloma is a disease of the elderly, with a median age at diagnosis of 69 years and characterized by intrinsic clonal heterogeneity. Almost all patients eventually will relapse, and patients with a high-risk cytogenetic profile, extramedullary disease or refractory disease have the worst outcomes. The introduction of Proteasome Inhibitors, Immunomodulatory agents and CD38 targeted therapies has resulted in higher Response Rates, as well as longer Progression Free Survival (PFS) and Overall Survival (OS), with the median survival for patients with myeloma approaching 10 years or more. Nonetheless, multiple myeloma in 2023 remains an incurable disease. With the introduction of new combinations of antimyeloma agents in earlier lines of therapy, patients with Relapsed or Refractory myeloma often have disease that is refractory to multiple drugs. There is an urgent unmet medical need for agents with novel mechanisms of action that are safe and effective, for patients with aggressive and resistant disease.
Daratumumab (DARZALEX®) is a human IgG1 antibody that targets CD38, a transmembrane glycoprotein abundantly expressed on malignant plasma cells and with low levels of expression on normal lymphoid and myeloid cells. DARZALEX® exerts its cytotoxic effect on myeloma cells by multiple mechanisms, including Antibody Dependent Cellular Cytotoxicity (ADCC), Complement Mediated Cytotoxicity and direct apoptosis. Additionally, DARZALEX® may have a role in immunomodulation by depleting CD38-positive regulator Immune suppressor cells, and thereby expanding T cells, in patients responding to therapy. Previously published Phase I and II studies involving patients with Relapsed or Refractory multiple myeloma demonstrated promising efficacy of DARZALEX® when given as a single agent, as well as when given along with Lenalidomide (REVLIMID®) and Dexamethasone.
POLLUX is a multicenter, randomized, open-label, active-controlled, Phase III trial in patients with Relapsed or Refractory multiple myeloma. In this study, 569 patients who had Relapsed or Refractory multiple myeloma were assigned in a 1:1 ratio to receive either DARZALEX®, REVLIMID® and Dexamethasone (D-Rd group, N=286) or REVLIMID® and Dexamethasone (Rd group, N=283). Patients refractory to REVLIMID® were excluded. Patients in the DARZALEX® group received DARZALEX® 16 mg/kg IV on days 1, 8, 15, and 22 of a 28 day cycle for 8 weeks during cycles 1 and 2, every 2 weeks (on days 1 and 15) for 16 weeks (cycles 3 thru 6), and every 4 weeks thereafter. Both treatment groups received REVLIMID® 25 mg PO on days 1-21 of each cycle and Dexamethasone 40 mg PO weekly. The Primary end point was Progression Free Survival (PFS). Secondary end points included Overall Survival (OS), Time to disease progression, Response Rate, Time to response, Duration of Response, and percentage of patients with results below the threshold for Minimal Residual Disease (MRD). Minimal Residual Disease status was evaluated for patients who had a Complete Response by Next-Generation sequencing assay of bone marrow.
At a median follow-up of 13.5 months, the PFS at 12 months was 83.2% in the DARZALEX® group compared to 60.1% in the control group (HR=0.37; P<0.001). The Overall Response Rate was significantly higher in the DARZALEX® group than in the control group (92.9% versus 76.4%, P<0.001) and further, there was a higher rate of Complete Response or better (43.1% vs. 19.2%, P<0.001). In the DARZALEX® group, 22.4% of the patients had results below the threshold for MRD (1 tumor cell per 105 white cells), as compared with 4.6% of those in the control group (P<0.001).
The authors in this publication reported updated efficacy and safety results at the time of final Overall Survival (OS) analysis of POLLUX, after a follow-up of more than 6.5 years. After positive primary analysis and protocol amendment, patients receiving Rd were offered DARZALEX® monotherapy after disease progression. At a median follow-up of 79.7 months, D-Rd significantly prolonged OS, with a 27% reduction in the risk of death compared to Rd alone (median 67.6 versus 51.8 months, respectively; HR=0.73; P=0.0044). Prespecified analyses demonstrated an improved OS with D-Rd versus Rd in most subgroups, including patients age 65 years or older and patients with one, two, or three prior lines of therapy, International Staging System Stage III disease, high-risk cytogenetic abnormalities, and refractoriness to their last prior line of therapy or a Proteasome Inhibitor. MRD negativity rates in this final analysis were nearly five times higher with D-Rd versus Rd (33.2% versus 6.7%) and regardless of the treatment group, MRD negativity was associated with improved OS, emphasizing the importance of achieving MRD negativity.
The most common Grade 3/4 treatment-emergent adverse events with D-Rd versus Rd were neutropenia, anemia, pneumonia, thrombocytopenia and diarrhea. Even though the incidence of Grade 3/4 infections was higher with D-Rd versus Rd, the discontinuation rate was similar in both treatment groups. No new safety concerns were observed with longer follow up.
It was concluded that in this updated analysis of the POLLUX study, DARZALEX® in combination with REVLIMID® and Dexamethasone significantly extended Overall Survival compared to REVLIMID® and Dexamethasone, in patients with Relapsed or Refractory multiple myeloma. The authors added that the POLLUX study reported the longest median Overall Survival observed to date in Phase III studies of REVLIMID® and Dexamethasone-based triplets in Relapsed or Refractory multiple myeloma. These results complement and strengthen the Overall Survival data recently reported with DARZALEX® plus VELCADE® (Bortezomib) and Dexamethasone in the Phase III CASTOR study in Relapsed or Refractory multiple myeloma.
Overall Survival With Daratumumab, Lenalidomide, and Dexamethasone in Previously Treated Multiple Myeloma (POLLUX): A Randomized, Open-Label, Phase III Trial. Dimopoulos MA, Oriol A, Nahi H, et al. J Clin Oncol 2023;41;1590-1599
