Responses and Survival Are Not Affected by Cytogenetics In Patients with Relapsed and Refractory Multiple Myeloma (R/R MM) Treated with Single-Agent Carfilzomib

The impact of cytogenetic abnormalities on the response to therapies and survival in patients (pts) with multiple myeloma (MM) has been well established in the literature. Bortezomib (BTZ), either alone or in combination with other agents, has been shown to overcome the adverse impact of several common unfavorable cytogenetic features. In addition, responses with lenalidomide (LEN)/dexamethasone and pomalidomide have also been reported in patients with unfavorable cytogenetic profiles. Carfilzomib (CFZ) is a novel and highly selective epoxyketone proteasome inhibitor which produces durable single-agent activity in pts with R/R MM. The objective of this analysis was to evaluate the influence of cytogenetics in a large Ph 2b study (PX-171-003-A1), with single-agent CFZ in pts with R/R MM.

Of the 266 pts enrolled in the 003-A1 study, 229 pts (86%) were response evaluable and had available metaphase cytogenetics and/or fluorescence in situ hybridization (FISH) analyses for hypodiploidy, chromosome 13 deletions, del 17p13, t(4:14), and t(14;16) chromosomal abnormalities. Metaphase cytogenetic analyses were available for 200 pts (75%) and FISH results were available for 205 pts (77%). All pts received CFZ at 20 mg/m² IV on days 1, 2, 8, 9, 15, and 16 in a 28-day cycle (C) in C1 followed by 27 mg/m² in each C thereafter for up to 12 C. Pts who completed 12 C of therapy were eligible to continue CFZ on an extension study. For the analysis, overall response rate was defined as ≥PR by International Myeloma Working Group (IMWG) criteria. Clinical benefit response (CBR; ORR + MR as defined by EBMT criteria) was also assessed. All responses were assessed and confirmed by an Independent Response Review Committee (IRC).

The median age in this subpopulation was 64 yrs. Pts must have had disease that was relapsed after ≥2 regimens including BTZ and either thalidomide (THAL) or LEN, and must have been refractory to their most recent regimen. In this heavily pre-treated pt population, pts had received median of 13 prior anti-myeloma drugs and a median of 5 prior regimens. 99.6% of pts had previously received treatment with BTZ, 74% received prior thalidomide, 94% prior lenalidomide, and 74% prior stem cell transplantation. The ORR (≥PR) for the pts with available metaphase cytogenetics and/or FISH analyses was 25% and the CBR (≥MR) was 38%. 71 of 229 pts (31%) had at least one cytogenetic abnormality. Of these, 27/71 (38%) pts had abnormalities detected via metaphase cytogenetics, 24 (34%) pts were detected by FISH and 20 (28%) pts had abnormalities by both methods. The presence of deletion 13 or hypodiploidy by cytogenetics or del17p13, t(4;14), or t(14;16) by FISH did not significantly impact the ORR. Specifically, 30% of pts with ≥1 abnormality responded compared to 23% with none. The CBR was also unaffected at 34% vs. 39% for pts with ≥1 and no abnormalities, respectively.

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For all pts in this analysis, the median duration of response (DOR) was 8 months (95% CI 6–10). For pts with ≥1 abnormality, the DOR was 7 months (95% CI 4–10) and did not differ significantly from the DOR of 8 months (95% CI 6–not reached) in pts with no abnormalities. A complete breakdown of response categories and time-to-progression (TTP) will also be presented.

CFZ demonstrated durable and comparable activity in pts with R/R MM in both the absence or presence of one or more cytogenetic abnormalities including hypodiploidy, chromosome 13 deletions, del 17p13, t(4:14), or t(14;16). Notably, these results are consistent with data obtained in another Ph2 study with CFZ in pts with relapsed MM following 1–3 prior therapies and who had abnormal cytogenetics (PX-171-004). The results of the present study suggest that durable responses to CFZ can be achieved in heavily pretreated patients and responses are not impacted by poor prognostic cytogenetic features.

Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Martin:Celgene: Honoraria; Onyx: Consultancy. Singhal:Celgene: Speakers Bureau; Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Onyx : Research Funding. Wang:Celgene: Research Funding; Onyx: Research Funding; Millenium: Research Funding; Novartis: Research Funding. Vij:Onyx: Honoraria. Jagannath:Millenium, OrthoBiotec, Celgene, Merck, Onyx: Honoraria; Imedex, Medicom World Wide, Optum Health Education, PER Group: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Lonial:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Kukreti:Celgene: Honoraria; Roche: Honoraria; Ortho Biotech: Honoraria. Bray:Onyx Pharmaceuticals: Employment. Vallone:Onyx Pharmaceuticals: Employment. Kauffman:Onyx Pharmaceuticals: Employment. Siegel:Millenium: Consultancy, Honoraria; Celgene: Consultancy, Honoraria.