Patient-reported outcomes in relapsed/refractory multiple myeloma treated with melflufen plus dexamethasone: analyses from the Phase II HORIZON study

Relapsed/refractory multiple myeloma (RRMM) is known to have a high burden of disease and complications associated with refractoriness to prior lines of therapy. Severe pain and fatigue symptoms and impairments in physical and emotional functioning have been strongly linked to reduced health‐related quality of life (HRQoL) in patients with RRMM. Assessment of patient reported‐outcome measures from the pivotal, Phase II HORIZON study (OP‐106; NCT02963493) in patients with RRMM (n = 64) demonstrated that melphalan flufenamide (melflufen) plus dexamethasone treatment preserved HRQoL. Patients had clinically meaningful improvements, even after eight treatment cycles, in relevant scales such as global health status/QoL, physical functioning, emotional functioning, pain, and fatigue. Patients with triple‐class–refractory disease (n = 50) displayed similar improvements. Patient‐reported outcome deterioration was delayed for a substantial amount of time in patients who experienced a response to melflufen plus dexamethasone treatment relative to patients who did not experience a response. These findings support the notion that treatment with melflufen plus dexamethasone may sustain or improve HRQoL over time in patients with RRMM, including in patients with triple‐class–refractory disease for whom outcomes are generally worse. The clinical benefits observed in patients from the HORIZON trial are encouraging and supportive of translation into real‐world practice.

Melflufen plus dexamethasone (dex) in patients (pts) with relapsed/refractory multiple myeloma (RRMM) exposed/refractory to prior alkylators: A pooled analysis of the O-12-M1 and HORIZON studies

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Background: Melphalan flufenamide (melflufen) is a first-in-class peptide-drug conjugate (PDC) that leverages aminopeptidases and rapidly releases alkylating agents inside tumor cells. Melflufen has a mechanism of action distinct from other alkylating agents (Slipicevic et al. AACR 2020. Abs. 1843). In the O-12-M1 (NCT01897714) and HORIZON (OP-106; NCT02963493) studies, melflufen plus dex showed meaningful efficacy and a clinically manageable safety profile in pts with RRMM (Richardson et al. Lancet Haematol. 2020;7:5; Richardson et al. J Clin Oncol. 2020;Dec 9 [Epub]). This pooled analysis examines pts from these studies exposed to prior alkylators. Methods: Both the O-12-M1 and HORIZON studies included pts with RRMM who received ≥ 2 prior lines of therapy (LoTs) and had a primary endpoint of overall response rate (ORR). Secondary endpoints included progression-free survival (PFS) and safety. Data from the 2 studies were pooled and analyzed according to previous exposure and refractoriness to alkylators before study entry. Refractoriness to prior alkylator therapy was defined as disease that failed to achieve a minimal response or progressed while on therapy, or within 60 d of last therapy. Results: Of 202 pts (HORIZON: n = 157, cutoff January 14, 2020; O-12-M1: n = 45, cutoff October 29, 2019), 178 (88%) had been exposed to alkylators in ≥ 1 prior LoT (see Table for subgroups). Pts exposed and refractory to alkylators in ≥ 2 LoTs had the highest number of pts refractory to an alkylator in the last LoT (61%), and 82% were refractory to an alkylator within 12 mo of study entry. Meaningful response rates were seen in all subgroups, except for pts who were exposed and refractory to alkylators in ≥ 2 prior LoTs (see Table). PFS trended toward being shorter with higher exposure and refractoriness to prior alkylators. Results should be interpreted with caution due to limited pt numbers. Grade 3/4 adverse events (AEs) were similar between pts exposed to prior alkylators (O-12-M1: 85%; HORIZON: 89%) and the overall population (O-12-M1: 84%; HORIZON: 89%). The most common AEs were hematologic, but were mostly reversible and clinically manageable. Nonhematologic AEs were infrequent and primarily grade 1/2. Conclusions: Melflufen in combination with dex showed meaningful efficacy and a clinically manageable safety profile in pts with RRMM exposed/refractory to prior alkylators. Clinical trial information: NCT02963493 and NCT01897714. [Table: see text]

Melflufen and Dexamethasone in Heavily Pretreated Relapsed and Refractory Multiple Myeloma

PURPOSE

Melphalan flufenamide (melflufen) is a first-in-class peptide-drug conjugate that targets aminopeptidases and rapidly and selectively releases alkylating agents into tumor cells. The phase II HORIZON trial evaluated the efficacy of melflufen plus dexamethasone in relapsed and refractory multiple myeloma (RRMM), a population with an important unmet medical need.

PATIENTS AND METHODS

Patients with RRMM refractory to pomalidomide and/or an anti-CD38 monoclonal antibody received melflufen 40 mg intravenously on day 1 of each 28-day cycle plus once weekly oral dexamethasone at a dose of 40 mg (20 mg in patients older than 75 years). The primary end point was overall response rate (partial response or better) assessed by the investigator and confirmed by independent review. Secondary end points included duration of response, progression-free survival, overall survival, and safety. The primary analysis is complete with long-term follow-up ongoing.

RESULTS

Of 157 patients (median age 65 years; median five prior lines of therapy) enrolled and treated, 119 patients (76%) had triple-class-refractory disease, 55 (35%) had extramedullary disease, and 92 (59%) were refractory to previous alkylator therapy. The overall response rate was 29% in the all-treated population, with 26% in the triple-class-refractory population. In the all-treated population, median duration of response was 5.5 months, median progression-free survival was 4.2 months, and median overall survival was 11.6 months at a median follow-up of 14 months. Grade ≥ 3 treatment-emergent adverse events occurred in 96% of patients, most commonly neutropenia (79%), thrombocytopenia (76%), and anemia (43%). Pneumonia (10%) was the most common grade 3/4 nonhematologic event. Thrombocytopenia and bleeding (both grade 3/4 but fully reversible) occurred concomitantly in four patients. GI events, reported in 97 patients (62%), were predominantly grade 1/2 (93%); none were grade 4.

CONCLUSION

Melflufen plus dexamethasone showed clinically meaningful efficacy and a manageable safety profile in patients with heavily pretreated RRMM, including those with triple-class-refractory and extramedullary disease.

HORIZON (OP-106): An exploratory analysis of time-to-next treatment (TTNT) in patients (pts) with relapsed/refractory multiple myeloma (RRMM) who received melflufen plus dexamethasone (dex)

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Background: Melflufen is a novel peptide-drug conjugate that rapidly delivers a cytotoxic payload into tumor cells. Melflufen + dex showed efficacy and a manageable safety profile in pts with poor-risk, heavily pretreated RRMM in the phase 2 HORIZON study (Mateos et al. ASH 2019. Abs. 1883). For pts with RRMM, longer TTNT is indicative of disease stabilization and clinical benefit and is associated with lower costs (Chen et al. J Manag Care Spec Pharm. 2017). This report of TTNT after melflufen + dex from HORIZON is, to our knowledge, the first report from a trial population with such advanced RRMM. Methods: Pts with RRMM who had received ≥2 prior lines of therapy, including an IMiD and a proteasome inhibitor (PI), and were refractory to pomalidomide and/or an anti-CD38 monoclonal antibody (mAb), received melflufen 40 mg (IV on d1 of each 28-d cycle) + dex 40 mg/wk until disease progression or unacceptable toxicity. The primary endpoint was overall response rate. Secondary endpoints included progression-free survival (PFS) and safety. TTNT was defined as the time from start of melflufen + dex to first subsequent therapy. Results: Overall, 154 pts were treated (data cutoff, Oct 1, 2019); median age was 64.5 y (range, 35-86), 32% had International Staging System stage 3 disease, 38% had high-risk cytogenetics, 32% had extramedullary disease (EMD), the median number of prior therapies was 5 (range, 2-12), and 71% had triple-class refractory MM (IMiD + PI + anti-CD38 mAb). Treatment discontinuation occurred in 108 pts (70%), most commonly due to disease progression (47%) and adverse events (14%). Among 125 pts evaluable for response, with a median follow up of 15.3 mo, the median TTNT was 8.0 mo (95% CI, 7.2-8.9) and the median PFS was 4.2 mo (95% CI, 3.7-4.9). TTNT and PFS were similar in subgroups of pts with triple-class refractory MM and EMD (Table). Subsequent therapies after melflufen + dex will be presented. Conclusions: TTNT in HORIZON (median 5 prior lines) was consistent with previous reports of TTNT in pts with RRMM who received melflufen + dex or other therapies (median 2-4 prior lines) (Bringhen et al. J Clin Oncol. 2019. Abs. 8043). Melflufen + dex is being further evaluated in the phase 3 OCEAN study (NCT03151811) in pts with RRMM who are refractory to lenalidomide. Clinical trial information: NCT02963493. [Table: see text]

Abstract CT154: Melflufen in patients (pts) with relapsed/refractory multiple myeloma (RRMM) refractory to daratumumab (dara) and/or pomalidomide (pom) (OP-106)

Background: Melflufen is an alkylating peptide belonging to a novel class of peptidase-enhanced compounds. Aminopeptidases are heavily overexpressed and key for the transformation process in multiple myeloma (MM). Melflufen selectively targets MM through aminopeptidase-driven accumulation, leading to a 50-fold enrichment of alkylating metabolites vs melphalan (Chauhan et al. Clin Can Research. 2013).

In the Phase I/II O-12-M1 study, melflufen showed activity in pts with RRMM (overall response rate [ORR], 31%; median progression-free survival [PFS], 5.7 mo; median overall survival, 20.7 mo), with acceptable safety (Richardson et al. Blood. 2017).

The Phase II HORIZON study evaluates melflufen in pts exposed to IMiDs and proteasome inhibitors (PIs) and refractory to pom and/or dara.

Methods: Pts with RRMM must have received ≥2 prior lines of therapy and have been exposed to IMiDs and PIs and refractory to pom and/or dara. Pts receive 40 mg melflufen intravenously on Day 1 of each 28-day cycle + 40 mg weekly dexamethasone. The primary endpoint is ORR (≥ partial response; investigator assessed per International Myeloma Working Group criteria). Secondary endpoints include clinical benefit rate (CBR; ≥ minimal response), PFS, and safety. Pts are treated until progressive disease (PD) or unacceptable toxicity.

Results: As of 22 Oct 2018, 83 pts were treated. Median age was 63 y (35-86), median time since diagnosis was 6.5 y (0.75-25); 36% of pts were International Staging System (ISS) stage 3 and 61% had high-risk cytogenetics at study entry. Median no. of prior lines was 5 (2-13). All pts were pom or dara refractory, 60% were pom and dara refractory and 86% were double refractory (IMiD and PI). Also, 84% had received prior alkylator therapy (55% alkylator refractory); 69% had received ≥1 prior transplant.

Treatment was ongoing for 23% of pts and discontinued in 77% of pts due to PD (57%), adverse event (AE; 13%), or other (7%). Treatment-related grade 3/4 AEs were reported in 62 (75%) pts, mostly hematologic: neutropenia (61%), thrombocytopenia (59%), and anemia (25%). Treatment-related non-hematologic grade 3/4 AEs were rare (eg, infections in 7% of pts). Fourteen (16%) pts experienced treatment-related serious AEs, most commonly febrile neutropenia (n=5), neutropenia (n=3), and thrombocytopenia (n=2). No treatment-related deaths were reported.

In total, 82 pts were evaluable for response: ORR was 33% and CBR 39%. Benefit was observed for high-risk subgroups: ORR for pts with ISS stage 3, high-risk cytogenetics, and double- and dara-refractory disease was 24%, 22%, and 19%, respectively. Median PFS was 4.0 mo (95% CI, 3.3-5.1).

Conclusion: Melflufen has promising activity in heavily pretreated, multi-refractory late-stage pts with RRMM. Melflufen was generally well tolerated with infrequent non-hematologic AEs and low rates of discontinuation due to AEs.

Citation Format: Paul G. Richardson, Albert Oriol, Alessandra Larocca, Paula Rodriguez Otero, Jan Moreb, Joan Bladé, Hani Hassoun, Michele Cavo, Adrián Alegre, Amitabha Mazumder, Christopher Maisel, Agne Paner, Xavier Leleu, Jeffrey A. Zonder, Johan Harmenberg, Sara Thuresson, Hanan Zubair, María-Victoria Mateos. Melflufen in patients (pts) with relapsed/refractory multiple myeloma (RRMM) refractory to daratumumab (dara) and/or pomalidomide (pom) (OP-106) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT154.

Simultaneous presentation of two distinct plasma cell neoplasms

Plasma cell neoplasms consist of a spectrum of diseases characterized by monoclonal proliferations of plasma cells. We report the simultaneous presentation of two distinct plasma cell neoplasms, a very uncommon situation.

Haematological complete remission by ponatinib and bortezomib in a patient with relapsed, Ph⁺ pre-B acute lymphoblastic leukaemia

A 74-year-old man was previously diagnosed with BCR-ABL1-positive pre-B cell acute lymphoblastic leukaemia (pre-B ALL) based on bone marrow cytology, flow cytometry, cytogenetics and fluorescent in situ hybridisation findings. Following a highly complicated hospital course, the patient achieved cytogenetic remission by consolidated chemotherapy and the tyrosine kinase inhibitor dasatinib. He subsequently presented with relapsed pre-B ALL after 3 years in remission. In consideration of his challenging clinical history, he was started on concurrent ponatinib (45 mg daily) and bortezomib (1.3 mg/m(2) intravenous weekly). The major molecular response was achieved (<0.0893% BCR-ABL1 transcripts) after 3 months. Bone marrow now demonstrates a BCR-ABL1-negative, complete cytogenetic response. The patient continues to do well with mild thrombocytopenia and improved anaemia on bortezomib and 30 mg daily ponatinib. Our experience with a single patient suggests the feasibility of combined targeted therapy with ponatinib and bortezomib. This novel treatment approach achieved clinical remission with a manageable toxicity profile.

Report of a phase II study of clofarabine and cytarabine in de novo and relapsed and refractory AML patients and in selected elderly patients at high risk for anthracycline toxicity

PURPOSE

To determine the efficacy and safety of clofarabine and cytarabine (Ara-C) in adult patients with relapsed or refractory acute myeloid leukemia (AML) and in elderly patients with untreated AML and heart disease.

PATIENTS AND METHODS

Patients with relapsed/refractory AML and older patients for whom there was a concern over toxicity from additional anthracyclines received 5 days of clofarabine, 40 mg/m(2) per day i.v. over 1 hour, followed 4 hours later by Ara-C, 1,000 mg/m(2) per day i.v. over 2 hours.

RESULTS

Thirty patients were enrolled. The median age was 67 years (range, 38-82 years) and 18 (60%) had received at least one prior therapy. Eleven (37%) patients had a history of cardiovascular disease and were considered to be at high risk for anthracycline toxicity. High-risk cytogenetic abnormalities were present in 14 (47%) patients. The overall response rate (complete remission [CR] plus partial remission) was 53%, including a CR in 14 patients (47%). Responses were observed in all cytogenetic risk groups and in patients who had received up to five prior therapies. The median disease-free survival interval was 9.5 months. The 30-day mortality rate was 20% (de novo AML, 8%; relapsed/refractory AML, 28%). Of the 14 patients achieving a CR, half were able to proceed to curative hematopoietic stem cell transplantation.

CONCLUSIONS

Clofarabine in combination with Ara-C is effective in both untreated and previously treated patients with AML. In addition, it represents a useful remission induction strategy to serve as a bridge to transplantation in older patients with AML.

Phase II study of clofarabine and cytosine arabinoside in adult patients with relapsed AML and in elderly patients with untreated AML who are at high risk of anthracycline toxicity

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Purpose: To evaluate the efficacy/safety of a novel AML regimen in elderly patients with heart disease or in patients with a contraindication to ‘standard‘ anthracycline-containing regimens. Patients and Methods: Phase II, open-label design. Eligible pts had elderly de-novo or relapsed AML or would not benefit from 7+3 or simlar therapy. Treatment was CLOF 40 mg/m2, Ara-C 1,000 mg/m2. (d1–5). Results: Patients were accrued and treated from April 2005 through Oct 2006. All pts signed IRB-approved consents. The median age was 67 years (range 38–82 years). Twenty (67%) subjects had received at least one prior cytoxic regimen (excluding 5-AZA). Significant cardiovascular (history of MI, bypass grafting, cardiomyopathy) was present in 43% (13/30) prior to therapy. Thirty pts were enrolled and all recieved at least one day of therapy. 1 pt died within 24 hours of starting treatment due to disease progression. Of the remaining, 29/30 received at least one complete cycle of therapy and 5 received 2 cycles. None received more than 2 cycles. Toxicities were greater in those receiving a second cycle. Grade 4 neutropenia developed in all patients. There were no cases of regimen-related cardiac toxicity. Most patients had some degree of edema and third-spacing syndrome. Several developed a significant but reversible acral rash. 25 patients survived >28 days and are evaluable for hematologic response. The histologic response rate (RR) is 68% (17/25) consisting of 14 (56%) complete remissions (marrow blasts <5%) and 3 (12%) partial responses (PR). There were 13 subjects with known cytogenetic abnormalities, 1 favorable and 12 unfavorable. Complete cytogenetic remissions (CytoCR) occurred in 4 of those patients, by chromosome analysis and/or FISH. Durable remissions and low toxicity allowed some patients to proceed to nonablative allogeneic stem cell transplantation. Conclusion: Clofarabine and Ara-C is an active and well tolerated regimen in myeloid malignancies including “elderly AML” a distinct entity usually associated with poor response rate and high treatment-related toxicities. Other drug combinations with clofarabine are ongoing in hematopoietic transplant and other high risk subgroups.

No significant financial relationships to disclose.

O6-benzylguanine and BCNU in multiple myeloma: a phase II trial

PURPOSE

Carmustine (BCNU) is known to have modest activity in multiple myeloma; however, resistance to BCNU manifests by the activity of O6-methylguanine methyltransferase (MGMT). The objective of this study was to determine the safety and efficacy of depletion of MGMT activity in plasma cells using O6-benzylguanine (O6-BG) with BCNU in patients with multiple myeloma.

METHODS

Patients with previously treated or untreated multiple myeloma were eligible. Cycles of O6-BG at a dose of 120 mg/m2 and BCNU at a dose of 40 mg/m2 were repeated every 6 weeks.

RESULTS

Seventeen patients were enrolled on the study, with a median follow-up of 24.5 (range 5-69) months. One complete response (7%) and 3 partial responses (20%) were observed. Nine patients (60%) had stable disease. Bone marrow studies demonstrated 94% depletion of MGMT activity in CD38+ marrow cells. The most frequent grade 3 and 4 adverse events were neutropenia (71%), lymphocytopenia (53%), and thrombocytopenia (53%).

CONCLUSIONS

Chemotherapy utilizing the MGMT inhibitor O6-benzylguanine and BCNU results in inhibition of MGMT activity in malignant plasma cells and produces meaningful responses in a modest proportion of patients with multiple myeloma. Hematologic toxicity with this regimen is significant and dose-limiting.