Emerging Quadruplets, Novel Targets, and Immunotherapy Advances Personalized Medicine in Multiple Myeloma

Thomas G. Martin, MD

Optimal treatment for patients with multiple myeloma is in constant flux with ongoing research regarding novel quadruplet regimens, the integration of options for lenalidomide (Revlimid)-refractory individuals, and the emergence of FDA-approved agents for triple-class refractory disease, said Thomas G. Martin, MD, who added that immunotherapies in development, such as bispecific T-cell engagers (BiTEs), will further this effort.

“The future is quite bright for multiple myeloma. We are really homing in on the best regimen for frontline therapy in transplant-eligible and -ineligible [patient populations],” Martin said. “We are also closer with our recommendations to figuring out how to treat early-relapsed multiple myeloma. We have a variety of novel drugs that are approved for use to treat [patients with] late relapse. That [setting] has been our unmet medical need, [historically].”

Martin, a clinical professor of medicine in the Adult Leukemia and Bone Marrow Transplantation Program; associate director of the Myeloma Program; and co-leader of the Cancer Immunology and Immunotherapy Program at the Helen Diller Family Comprehensive Cancer Center of the University of California, San Francisco; added that there are “several very exciting therapies” under investigation in clinical trials, including BiTEs. “[These therapies] are showing unprecedented responses in very refractory patients, [including] the triple-class exposed patients, which is amazing.”

He spoke with OncLive^® during an Institutional Perspectives in Cancer webinar on multiple myeloma. He chaired the virtual meeting which covered updates in frontline, early-, and late-relapsed multiple myeloma, immunotherapy in multiple myeloma, and frontline and relapsed/refractory amyloidosis.

Martin discussed the latest news in frontline, early relapsed, and heavily pretreated multiple myeloma, including the growing promise of quadruplets, emerging targets beyond BCMA, and the potential emergence of quadruplets, venetoclax (Venclexta), and antiviral therapy in amyloidosis.

OncLive^®: How will the field integrate quadruplet-based therapies for transplant-eligible and -ineligible patients with multiple myeloma in the frontline setting?

Martin: For frontline therapy in multiple myeloma, we break [our algorithm] up [according to] patients who are fit and [unfit. Patients who are fit] can likely go to stem cell transplant. A quadruplet is going to be where we are headed, and it is going to be [a quadruplet using] the 3 different classes of drugs: a monoclonal antibody, an immunomodulatory drug [IMiD], and a proteasome inhibitor [PI], together with a steroid. [The combination of] those 4 classes of drugs [were evaluated] in the GRIFFIN [NCT02874742] and Cassiopeia trials [NCT02541383]. The GRIFFIN trial looked at daratumumab [Darzalex], lenalidomide [Revlimid], bortezomib [Velcade], and dexamethasone, whereas the Cassiopeia trial looked at daratumumab, thalidomide [Thalomid], and dexamethasone. Both [trials] showed spectacular early responses for induction therapy to [the respective] quadruplets.

Another study looked at daratumumab [plus] carfilzomib [Kyprolis], lenalidomide, and dexamethasone [KRd]. That trial too showed unprecedented early responses as frontline therapy. More studies are looking at other CD38[-directed monoclonal antibodies], like isatuximab-irfc [Sarclisa], together with lenalidomide, as well as KRd.

These quadruplets are showing fast and deep responses after 4 cycles [of treatment]. For patients who are transplant eligible, [treatment with a quadruplet] prepares them for transplant quite well. They can go into transplant with a nice, deep response and, hopefully, [derive] a deeper response after remission.

The question exists of whether the quadruplets and other therapies may take away the need for autologous stem cell transplant. Right now, transplant is still part of frontline therapy and is especially useful in patients who have high-risk disease.

In the transplant-ineligible population, the MAIA trial [NCT02252172] looked at daratumumab plus lenalidomide and dexamethasone vs lenalidomide and dexamethasone. The triplet has shown a median progression-free survival [PFS] approaching 60 months; that is just amazing for frontline therapy. We will see if quadruplets are needed in the transplant-ineligible setting.

We have several trials testing quadruplet therapy in the transplant-eligible population. Both daratumumab and isatuximab are being combined with IMiDs, PIs, and dexamethasone in a randomized fashion [vs triplet therapy]. We will see what the winner is. It will be interesting as we move forward, but right now, if we start that triplet therapy, we expect a PFS of 60 months, which is just amazing.

What treatment considerations need to be considered when selecting a combination for patients with early-relapsed multiple myeloma?

When we think about early relapse, what becomes important is what patients were on when they became relapsed or refractory. If they were on an IMiD, most of the time it was lenalidomide as maintenance therapy. We would then consider that patient lenalidomide refractory. In that scenario, we would use a CD38[-directed monoclonal antibody] plus pomalidomide [Pomalyst] and dexamethasone or a CD38[-directed monoclonal antibody] plus a PI and dexamethasone.

The data with daratumumab plus pomalidomide and dexamethasone, as well as isatuximab plus pomalidomide and dexamethasone, are quite good. Truthfully, my favorite [approach] is that if the patient is on an IMiD, I give an antibody together with a PI. The IKEMA [NCT03275285] and CANDOR [NCT03158688] studies have shown deep and durable responses with a CD38[-directed monoclonal antibody] plus carfilzomib and dexamethasone in the early-relapsed setting.

The CANDOR study showed a PFS of about 28 months. We still need longer follow-up from the IKEMA study to see what the PFS is going to be, but it is certainly going to be at least 28 months. Specifically, [in the IKEMA] study we showed that 30% of patients had achieved minimal residual disease [MRD] negativity with the triplet combination in the early-relapsed setting. It’s unprecedented to see these deep responses with evidence of MRD negativity.

If patients have not received a CD38[-directed monoclonal antibody] as part of frontline therapy, that is what the first component should be to add for first relapse. The other regimens, which we’ve used before and are good, include pomalidomide, bortezomib, and dexamethasone, or pomalidomide, carfilzomib, and dexamethasone. There are multiple other choices, but those are my favorites.

What options are available to treat patients with triple-class refractory multiple myeloma?

In early-to-mid relapse, we usually use a ping-pong approach where we go back and forth between the categories of agents. Eventually, after 2 or 3 lines of therapy, patients have been exposed to what I call the big 5, which are lenalidomide, bortezomib, carfilzomib, pomalidomide, and a CD38-directed antibody. This is a setting which had been our unmet medical need.

We now have 3 agents that are FDA approved for that group of patients. We have selinexor [Xpovio] plus dexamethasone, which was approved based on the STORM trial [NCT02336815]. That doublet can be used in the [originally indicated] twice-weekly [dose], or given once weekly, which is much better tolerated. Often, we combine [selinexor] with another agent, such as bortezomib, carfilzomib, pomalidomide, or, even, daratumumab, so it is a kind of pick-your-partner [agent] in that regard. There are toxicities associated with selinexor, and we must follow patients closely. We can’t just give them the therapy and see them in 4 weeks. We must follow their sodium closely because some patients need salt replacement, hydration, and anti-emetics.

The second [agent approved for triple-class refractory multiple myeloma] is belantamab mafodotin-blmf [Blenrep], which is an antibody-drug conjugate that targets BCMA. The poison is MMAF, which is associated with thrombocytopenia and ocular toxicity. We found that when belantamab mafodotin is used as a single agent without a steroid, the response rate was just over 30%. Patients who respond have durable responses upward of 10 or 12 months. We just have to watch patients for ocular toxicity because [belantamab mafodotin] can cause keratitis on the surface of the eye. Patients must see an ophthalmologist before each dose of belantamab mafodotin, which is dosed every 3 weeks. In my experience, [keratitis] usually occurs after the second or third dose. Most patients respond after the first or second dose, so we can see if the patient responds, and then continue or modify the regimen. We can lengthen the dose out to every 4 weeks or every 6 weeks or drop the dose from 2.5 mg/kg to 1.9 mg/kg.

Lastly, we have a new drug called melphalan flufenamide [melflufen; Pepaxto], which is a lipophilic, alkylator-based therapy. The lipophilic component gets the drug fast into cells, but it can be cleaved off the alkylator by aminopeptidases. In fact, normal cells don’t have many aminopeptidases, so [melflufen] gets in and out of normal cells relatively quickly; however, the drug gets in myeloma cells, the lipophilic component is cleaved off, and the alkylator gets trapped inside the cell. [Melflufen] is [administered as] one flat dose of 40 mg every 4 weeks with weekly dexamethasone. It is tolerable; the big adverse effect [AE] is blood count suppression. We’ve seen response rates in the 25% to 30% range.

Where does immunotherapy factor into the equation now that the CAR T-cell therapy idecabtagene vicleucel (ide-cel; Abecma) is FDA approved?

The newest [therapy] on the block in what is available for patients who have had 4 prior lines of therapy is the CAR T-cell therapy ide-cel. It is BCMA directed, the original vector was known as bb2121. It is now FDA approved.

The rollout [of ide-cel] has been a little slow in terms of slot allocation, and it has been difficult for centers across the country to get patients on slots. We are hoping that the slot availability will increase over the next few months.

That said, for patients who are triple-class refractory and have had 4 prior lines of therapy, [ide-cel] is a perfect therapy. The CAR T cells have to be done at a licensed CAR T-cell center, of which there are only about 70 in the United States. That comes with some overhead because patients must move to the center and remain there for the first 30 days of therapy because of the significant toxicities associated with CAR T-cell therapy. [These AEs] are mostly cytokine release syndrome [CRS], which happens 80% to 90% of the time, and some neurotoxicity, which is reported in around 15% to 20% of patients. Patients must be followed closely and require initial hospitalization between 7 to 14 days. Then, patients must stay local [for follow-up].

There is a lot of overhead, but it is a one-and-done treatment. We collect their T cells, give them lymphodepletion, give them back the T cells, and patients are off therapy. The median PFS for ide-cel is about 12 months, so hopefully patients get 12 months of free time where they don’t need therapy and have truly good quality of life, which is quite nice.

Would BiTEs offer a more convenient option for patients who are unable to make the commitment needed for CAR T-cell therapy administration?

The nice thing about immunotherapy is that multiple targets are being investigated. BCMA was our first target, but we have others, such as GPRC5D and FcRH5. We have multiple different CAR T-cell therapies currently in research studies to try to build upon ide-cel.

We also have BiTEs, in which one arm binds to BCMA or whatever the target is on the myeloma cell, and the other arm looks for the immune cell in the local environment. Most of the other arms bind to CD3 on T cells to activate the T cells. [BiTEs] are a little bit different in terms of how they bind to the myeloma cell and how much they activate the T cell by binding to CD3.

That said, in the early research, most of these therapeutics as single agents have shown response rates on the order of 60% to 80%. That’s, again, unprecedented for single agents. These therapeutics are quite impressive in terms of response rates, but they are also associated with CRS and mild neurotoxicity. They require initial dosing in the hospital and patients are usually hospitalized for 7 to 10 days for step-up dosing. After that, [treatment] can be done in the outpatient setting with intermittent dosing. BiTEs vary from dosing weekly and then less frequently to every 3 weeks. Coming back to the center every 3 weeks is reasonable, even for patients who live outside the research center.

In San Francisco, we have patients coming in every 3 weeks to get their therapy and then they head back home, which is nice. However, it is ongoing therapy and patients must continue their therapy rather than receive a one-and-done treatment. This is because BiTEs are off-the-shelf products. There is not a collection and manufacturing step. These drugs are going to be given in the community eventually once they are approved. These drugs will be used in many more patients compared with CAR T-cell therapy just because of the logistics of CAR T-cell therapies, so BiTEs are exciting.

Pivoting to amyloidosis, what are the most significant updates for this patient population?

These advances [observed in multiple myeloma] have also spilled over to amyloidosis. We now have great frontline therapy for amyloidosis, as well as many irons in the fire [evaluating] ways we can treat relapsed amyloidosis. We’ve had a troubled past [with] antiviral therapy in amyloidosis. However, there is renewed interest in this and, certainly, there are patients with amyloidosis who would benefit from antiviral therapy.

There is a lot of work going on in amyloidosis currently. The ANDROMEDA study [NCT03201965] has shown in randomized fashion that daratumumab plus bortezomib, cyclophosphamide, and dexamethasone [VCd] results in better organ response rates and PFS vs VCd alone, which had really been our standard therapy in amyloidosis. Going forward, patients with amyloidosis should receive this quadruplet as frontline therapy.

Patients with amyloidosis also have a high incidence of 11;14 translocations [t11;14]. Some case reports [have read out] of patients being treated with venetoclax. Ongoing research avenues are going to further investigate venetoclax with or without the combination of other drugs. Venetoclax will have a strong response rate in patients with amyloidosis and will be used for initial relapse. Eventually, [venetoclax] might be used in patients with t11;14, but those studies are being done. Approval for that is a long way down the road.

Also down the road for amyloidosis are BiTEs. BCMA is on the surface of plasma cells in amyloidosis, also, [as in multiple myeloma]. There is also a renewed interest in antiviral therapy in amyloidosis. The amyloid proteins deposit in the cell and cause significant organ toxicity, especially in the [heart] and kidneys. Antiviral therapy may enhance and quicken organ responses to improve survival for patients, including those with severe cardiac amyloidosis.