EXPERT ANALYSIS FROM ASH 2015
ORLANDO (FRONTLINE MEDICAL NEWS) – The moment the Food and Drug Administration approved daratumumab, ixazomib, and elotuzumab in rapid-fire succession over 15 days in November 2015, Dr. S. Vincent Rajkumar’s phone started ringing.
As with other multiple myeloma experts, three common questions kept cropping up:
• For previously untreated patients, should we add bortezomib to lenalidomide plus dexamethasone (Rd) based on the S0777 results?
• For previously treated patients, should we add ixazomib or elotuzumab to Rd?
• Should we add daratumumab to frontline therapy right out of the box?
Daratumumab (Darzalex), ixazomib (Ninlaro), and elotuzumab (Empliciti) are welcome additions to the armamentarium, but the problem with this plethora of riches is that numerous treatments already exist for frontline multiple myeloma, observed Dr. Rajkumar , professor of medicine at the Mayo Clinic in Rochester, Minn. In fact, the National Comprehensive Cancer Network guidelines list 22 possible newly diagnosed myeloma regimens that can be potentially recommended for patients.
“This definitely leads to confusion in the community. And this was the result of the fact that we didn’t have a single, good randomized trial with a survival benefit of a modern therapy against another modern therapy,” Dr. Rajkumar said at the annual meeting of the American Society of Hematology during a joint FDA/ASH symposium on the three newly approved agents.
This quandary was solved at ASH with phase III randomized data from the Southwest Oncology Group S0777 study showing a significant overall survival advantage with a triplet of bortezomib (Velcade), lenalidomide (Revlimid), and dexamethasone (VRd) followed by continuous Rd maintenance compared with Rd alone and ongoing maintenance in untreated patients who did not intend to receive stem cell transplant, he said.
Median overall survival was 75 months for the triplet vs. 64 months for the Rd doublet (hazard ratio, 0.709; two-sided log-rank P = .0250), and median PFS 43 months vs. 30 months (HR, 0.712; one-sided P = .0018), study author Dr. Brian Durie , of Cedars-Sinai Comprehensive Cancer Center in Los Angeles, reported ( Abstract 25 ).
The VRd triplet is already in use in the United States, but based on the S0777 results, many groups, including the Mayo Clinic, have changed treatment guidelines and now “prefer bortezomib, len-dex for frontline therapy, not just in transplant candidates, but also in non-transplant candidates,” Dr. Rajkumar said.
In countries where VRd is not possible, bortezomib, thalidomide, and dexamethasone (VTd) is a second option.
Rd is an appropriate therapy for non-transplant candidates who are frail or aged 75 years or older, he said, adding that there is no need to add bortezomib for patients already on Rd and doing well.
“If your patient is doing well on a doublet, leave them alone,” Dr. Rajkumar advised.
Similarly, for patients with relapsed myeloma who are doing well on Rd, there isn’t “an urgent need” to add ixazomib or elotuzumab, but rather, he said, “We can reserve those for when the patient progresses.”
Ixazomib is approved in combination with Rd after at least one prior therapy, but the oral proteasome inhibitor may have a role in the frontline treatment of standard-risk patients. It is a very simple regimen, just three pills a month, and “the side effect profile is outstanding; virtually difficult to tell who’s taking placebo and who’s taking drug,” Dr. Rajkumar observed.
In addition, some patients may not have access to bortezomib because of insurance reasons or can’t drive to the clinic once a week to get the shot, while others may be too frail to get an intravenous or subcutaneous shot or may have neuropathy.
“For whatever reason, I think it is reasonable to keep in mind that we may have a situation where we can use ixazomib/len-dex in clinical practice if the patient’s best interests so dictate,” he said.
For high-risk patients (deletion 17p or translocations t(4;14), t(14;16), t(14;20), VRd or VTd are obvious upfront choices. Based on four phase II trials and the ASPIRE results in the relapsed and refractory setting, however, the Mayo Clinic has already decided that the recently approved second-generation proteasome inhibitor carfilzomib (Kyprolis) plus Rd is also worth considering.
Adding a monoclonal antibody such as elotuzumab or daratumumab to a VRd triplet or ixazomib, lenalidomide, and dexamethasone (IRd) triplet may be another way to improve outcomes in high-risk patients, who still die with a median overall survival of 3 years, Dr. Rajkumar said. This strategy is already being used in the ongoing SWOG S1211 study.
For maintenance therapy after VRd or VTd and autologous stem cell transplant, he recommended lenalidomide for standard-risk patients and bortezomib-based maintenance for high-risk patients, but said ixazomib-based maintenance with the addition of monoclonal antibodies may also have a role in high-risk patients.
What may be more important going forward is how these three drugs will be used in clinical trials, Dr. Rajkumar observed.
“We’d rather put all patients on clinical trials than any of the recommendations I made,” he said. “The problem is that clinical trials have to be appropriately designed.”
Several phase III trials are already ongoing comparing a doublet versus a triplet (IRd vs. Rd, elotuzumab-Rd vs. Rd, and daratumumab-Rd vs. Rd) in the frontline setting, so the key question for future trials is which triplet: VRd, KRd, elotuzumab-Rd, or daratumumab-Rd, and to what endpoint.
Progression-free survival can remain a primary endpoint for comparing two triplets in the frontline, but PFS alone is not enough in the maintenance setting and investigators should look to other primary endpoints such as PFS2, PFS1 vs. PFS2, overall survival with a higher type 1 error than currently used, or PFS plus validated patient-reported or quality of life outcomes, Dr. Rajkumar said.
Speaking on how the three new agents fit into the relapsed or refractory space, Dr. Paul Richardson , of Dana-Farber Cancer Institute, Boston, said three-drug platforms are emerging as a standard of care for relapsed or refractory disease after studies have shown time and time again they are better than doublets.
He highlighted phase III data reported at ASH by Dr. Philippe Moreau from TOURMALINE-MM1 ( Abstract 727 ) showing a 35% improvement in PFS with weekly oral ixazomib plus lenalidomide-dexamethasone vs. Rd alone in relapsed and/or refractory multiple myeloma.
This translated into a median 6-month gain in PFS compared with an almost 9-month PFS benefit seen in ASPIRE with carfilzomib plus Rd, but cross-trial comparisons should be approached with some caution and both hazard ratios were very robust, he said. In addition, as previously observed, ixazomib is remarkably well tolerated.
“I think ixazomib, particularly in older patients and particularly in patients with high-risk disease, will be very useful in the context of the three-drug or even greater combinations. So there’s a strong rationale for its use,” Dr. Richardson said.
He went on to say that elotuzumab has shown remarkable anti-myeloma activity in the relapsed and refractory setting, improving both the overall response rate and PFS when used in combination with Ld vs. Ld alone in the ELOQUENT-2 trial. Updated results from ELOQUENT-2 were presented at the ASH meeting ( Abstract 28 ).
A PFS benefit was also seen when elotuzumab was added to bortezomib and dexamethasone, with a 24% reduction in the risk of disease progression or death reported in a study presented at ASH by myeloma expert Dr. Antonio Palumbo ( Abstract 510 ).
“My point in showing this is that when you think of elotuzumab being used with lenalidomide and dexamethasone in relapse, many of our patients are actually on them as maintenance when it occurs, therefore elotuzumab may have a role in combination, for example, with proteasome inhibitors in this same setting,” Dr. Richardson said.
Several pomalidomide-based triple therapy combinations have been evaluated in advanced relapsed or refractory myeloma, with a phase II study (Abstract 506) reported that morning at ASH showing the third-generation immunomodulatory drug (IMiD) pomalidomide induced responses in 60% of heavily pretreated patients when partnered with pembrolizumab and dexamethasone.
Combination strategies with daratumumab are also very provocative, particularly in the context of IMiDs, he noted. A phase Ib study reported in the same early morning session by Dr. Ajai Chari ( Abstract 508 ) had a “very encouraging” overall response rate of 71% with daratumumab plus pomalidomide and dexamethasone in heavily pretreated patients, including 43% very good partial responses or better, and an overall response rate of 67% among double-refractory patients.
“Daratumumab and elotuzumab, in my view, as first-in-class monoclonal antibodies, are paradigm-changing agents,” Dr. Richardson concluded. “They provide us with this mutation-driven ability to overdrive the impact of those mutations and the important point is that they prescribe an entirely non-crossresistant strategy that can be easily added to existing platforms of drugs.”
Dr. Rajkumar reported discussion of off-label drug use for elotuzumab, daratumumab, ixazomib, and carfilzomib in untreated myeloma, maintenance, and early relapse. Dr. Richardson reported membership on a board of directors or advisory committee for Millennium Takeda, Celgene, Janssen, Bristol-Myers Squibb, and Novartis, and research funding from Millennium Takeda and Celgene.