A Phase 1/2, Dose and Schedule Evaluation Study to Investigate the Safety and Clinical Activity of Belantamab Mafodotin Administered in Combination with Lenalidomide and Dexamethasone in Transplant-Ineligible Patients with Newly Diagnosed Multiple Myeloma
Authors: Terpos Evangelos , Gavriatopoulou Maria , Ntanasis-Stathopoulos Ioannis , Malandrakis Panagiotis , Fotiou Despina , Kanellias Nikolaos , Gkolfinopoulos Stavros , Manousou Kyriaki , Kastritis Efstathios , Dimopoulos Meletios A. 
Published: November 2021

Abstract
Background: The combination of lenalidomide with dexamethasone (Rd) represents a preferred treatment backbone for newly diagnosed, transplant-ineligible patients (pts) with multiple myeloma (MM), while the addition of a third drug (i.e., daratumumab, bortezomib, carfilzomib or ixazomib) leads to higher response rates and deeper responses. Belantamab mafodotin (belamaf; GSK2857916) is a multi-modal antibody-drug conjugate that has demonstrated a clinically meaningful anti-myeloma activity with a manageable safety profile in heavily pre-treated pts with relapsed or refractory MM. Preclinical evidence suggest a potential synergy between belamaf and lenalidomide; at the same time, these drugs do not have overlapping toxicities. Thus, there is strong rationale for investigating the clinical activity of upfront belamaf in combination with Rd in transplant-ineligible MM pts.
Aims: The present analysis evaluates the safety profile of belamaf in 3 different dosing schemes in combination with Rd in treatment-naïve, transplant-ineligible MM pts.
Methods: BelaRd (study short title) is an open-label, single-center, phase 1/2 study conducted in Greece, aiming to enroll 66 newly diagnosed, transplant-ineligible MM pts. The study comprises 2 parts. Part 1 will evaluate 3 doses of belamaf (2.5, 1.9, and 1.4 mg/kg) in combination with Rd, each given in an individual cohort of pts, and will determine the recommended phase 2 dose (RP2D). In this part, belamaf will be administered q8w and, depending on toxicity, dosing may be rescheduled to q4w or q12w. In Part 2, a single cohort of pts will be treated with belamaf in the RP2D in combination with Rd to further evaluate the safety and clinical activity of this regimen. Part 2 will also evaluate 2 different sets of guidelines for ocular adverse events (AEs) in 2 separate groups of pts to identify the optimal method for the management of belamaf-related keratopathy. This is the initial safety analysis of Part 1 and includes pts who received ≥1 belamaf dose and were followed up for ≥8 weeks.
Results: Overall, as of 16 July 2021 (cut-off date), 18 pts completed the dose-limiting toxicity (DLT) observation period, defined as specific ≥ grade 3 AEs occurring during the first cycle of study treatment, and were included in the safety analysis. The median age was 72 years (range: 65-82), and the majority of pts were male (55.6%). Lytic bone lesions were present in 12 (66.7%) pts; no pts had extramedullary disease. Most pts (9, 50.0%) had Eastern Cooperative Oncology Group performance status 0 followed by those at 1 (8, 44.4%) and 2 (1, 5.6%). Regarding the revised International Staging System, most pts (13, 72.2%) were at stage II, followed by those at stages III (2, 11.1%) and I (3, 16.7%); 3 (16.7%) pts had high-risk cytogenetics, defined as del17p13, t(4;14) or t(14;16). By the cut-off date, pts had received a median of 4 treatment cycles, with 17 (94.4%) pts still being on treatment; 1 (5.6%) pt died due to pneumonia, unrelated to the study treatment. 16 (88.9%) pts experienced ≥1 treatment emergent adverse event (TEAE). In total, 11 (61.1%) pts had ≥1 TEAE grade 3/4, of which 1 was related to belamaf; 1 (5.6%) pt experienced a serious adverse event (SAE). There were 2 cases of dose reduction and 1 case of dose delay. The most common grade 3/4 TEAEs were fatigue (5 pts, 27.8%) and rash (4 pts, 22.7%), all related to lenalidomide. One SAE was reported: pneumonia grade 5 in the 2.5 mg/kg cohort. DLTs were noted in 3 (16.7%) pts: 1 pt with grade 3 fatigue in the 1.4 mg/kg cohort and 1 pt with grade 3 rash in each of the 1.9 and 1.4 mg/kg cohorts, all related to lenalidomide.
Regarding belamaf-related ocular AEs, there were 2 cases of superficial punctuate keratopathy (grade 1 and 2 each, both in the 2.5 mg/kg cohort), 10 cases of decreased visual acuity (grade 1 [8 pts, 44.4%]: 4 in the 1.9 mg/kg cohort and 4 in the 1.4 mg/kg cohort; grade 2 [2 pts, 11.1%] in the 2.5 mg/kg cohort), and 1 case of grade 1 blurred vision in 2.5 mg/kg cohort.
Conclusions: In the first safety analysis of the BelaRd study no new safety signals for the belamaf-Rd combination were observed. The frequency of ocular AEs was within the anticipated range. This early analysis shows that the triplet combination can be safely administered in treatment-naïve, transplant-ineligible MM pts. The enrollment in the study is ongoing, and more safety and efficacy data will become available with the inclusion of additional pts in an updated analysis.

Disclosures
Terpos: Novartis: Honoraria; Sanofi: Consultancy, Honoraria, Research Funding; Janssen-Cilag: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Genesis: Consultancy, Honoraria, Research Funding; GSK: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; BMS: Honoraria. Gavriatopoulou: Janssen: Honoraria; Takeda: Honoraria; Karyopharm: Honoraria; GSK: Honoraria; Genesis: Honoraria; Sanofi: Honoraria; Amgen: Honoraria. Gkolfinopoulos: Health Data Specialists: Current Employment. Manousou: Health Data Specialists: Current Employment. Dimopoulos: Janssen: Honoraria; Beigene: Honoraria; Takeda: Honoraria; BMS: Honoraria; Amgen: Honoraria.