In a case that researchers hope might pave the way for similar responses, a hospice-bound relapsed/refractory multiple myeloma (RRMM) patient who relapsed after chimeric antigen receptor (CAR) T-cell therapy was brought back into remission with the help of next-generation genomic sequencing, targeted molecular analysis and a novel combination of MAP kinase (MAPK)–inhibiting drugs.
“We have shown that comprehensive molecular profiling of advanced myeloma patients may provide critical information to guide treatment beyond standard of care,” senior author Alessandro Lagana, PhD, of the Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, said in an interview.
Dr. Alessandro Lagana
“This represents proof of concept that, while not curative, targeted molecules may serve as potential bridging therapies to clinical trial enrollment,” the authors further report in the case study, published recently in the Journal of Hematology & Oncology.
The use of B-cell maturation antigen (BCMA) CAR T-cell therapy approaches has transformed the treatment of multiple myeloma and leukemias, resulting in high response rates. However, most patients ultimately relapse, and no clear treatment options beyond CAR T therapy are established.
Such was the case for a 61-year old patient described in the study, who had relapsed 6 months after undergoing anti-BCMA CAR T-cell therapy and progressed after being salvaged for a short period with autologous stem cell transplantation. The patient had developed skin extramedullary disease, manifested as subcutaneous nodules.
“The subcutaneous skin lesions in lower extremities made him [ineligible] for another clinical trial and left him with no options,” Dr. Lagana said.
Using next-generation whole-exome sequencing, Dr. Lagana and colleagues had observed that a previously identified BRAF V600E–dominant subclone had persisted, despite the CAR T-cell treatment, in the patient’s bone marrow and cutaneous plasmacytoma.
The finding was not uncommon. More than half of RRMM patients (about 53%) show emerging clones with mutations within the MAPK signaling pathway, and in about 7% of patients, those include BRAF V600E, which can be targeted, the authors noted.
Further assessment of the patient’s CD138-positive MM cells using western blot signaling pathway analysis looking at DNA and RNA markers did indeed show an increase in MAPK signaling as a consequence of the mutation. This suggested a potential benefit of triple MAPK inhibition, compared with standard strategies.
Based on that information and on insights the researchers had gained from previous research, they implemented the novel, orally administered triple-combination treatment strategy, consisting of monomeric inhibition of BRAF dabrafenib (100 mg, twice daily), as well as dimeric inhibition with the multi–kinase inhibitor regorafenib (40 mg, once daily) and a MEK inhibitor (trametinib, 1.5 mg, for 21/28 days daily).
Of note, previous efforts using only monomeric inhibition of BRAF have not shown much success, but early data has shown some potential, with the inclusion of dimeric inhibition.
“Monomeric inhibition of BRAF has been attempted in patients with V600E, but the efficacy has been limited, likely due to feedback activation of the MAPK pathway via induction of BRAF dimer formation,” Dr. Lagana explained.
Meanwhile, “previous in vitro data from our colleagues at Mount Sinai has shown that inhibition of both monomeric and dimeric forms of BRAF in combination with MEK inhibition can overcome the negative feedback and lead to more efficacious and tolerable treatment,” he said.
With the treatment, the patient achieved a very good partial response for 110 days, with prompt reduction of the subcutaneous skin lesions and an 80% reduction in lambda free light chain (27.5 mg/L).
The triple-drug combination was well tolerated with minimal side effects, primarily involving grade 1 fatigue, and the patient was able to carry out activities of daily living and return to work.
“The triple inhibition allowed us to use less of each drug, which resulted in a well-tolerated regimen without any significant side effects,” Dr. Lagana said.
While the patient relapsed about 3 months later, there was, importantly, no recurrence of the subcutaneous nodules.
“We believe that the triple MAPK inhibition completely eradicated the disease clones driving the extramedullary disease,” Dr. Lagana said.
The therapy meanwhile enabled the patient to bridge to a new clinical trial, where he went into complete remission, and still was as of Sept. 29.
“To our knowledge, this was the first reported successful case of this treatment in an RRMM patient,” Dr. Lagana explained.