Apollo: Phase 3 Randomized Study of Subcutaneous Daratumumab Plus Pomalidomide and Dexamethasone (D-Pd) Versus Pomalidomide and Dexamethasone (Pd) Alone in Patients (Pts) with Relapsed/Refractory Multiple Myeloma (RRMM)

Introduction

Immunomodulatory drug (IMiD)-based regimens are a standard of care (SOC) for RRMM. Daratumumab (DARA) is a CD38-targeted mAb approved for treatment of pts with RRMM. The subcutaneous (SC) formulation of DARA has a similar safety profile as intravenous DARA, with a statistically significant reduction in infusion-related reaction (IRR) rates and a considerably shorter administration duration of 5 mins. DARA SC is approved for use in the US, EU, Canada, and Korea.

In the phase 1b study of DARA plus the IMiD pomalidomide, D-Pd induced deep responses and was well tolerated in pts with heavily pretreated RRMM, including those with prior lenalidomide (len) treatment. D-Pd is approved in the US for RRMM pts with ≥2 prior lines of therapy, including len and a proteasome inhibitor (PI).

APOLLO (NCT03180736) is a phase 3 study conducted in collaboration between European Myeloma Network investigators and Janssen to evaluate DARA SC plus Pd vs Pd alone in RRMM pts who had received ≥1 prior line of therapy including len and a PI. We report the primary analysis of APOLLO.

Methods

In this open-label, multicenter study, eligible pts had RRMM and received ≥1 prior line of therapy including len and a PI, had responded to prior treatment and progressed on or after their last regimen; pts with only 1 prior line of therapy (1PL) were required to be refractory to len. Prior anti-CD38 or pomalidomide was not permitted. Pts were randomized 1:1 to Pd ± DARA SC. Stratification was based on International Staging System (ISS) disease stage (I, II, III) and number of lines of prior therapy (1, 2-3, ≥4).

All pts received 28-day treatment cycles (C). P: 4 mg (PO) QD on Days 1‑21; d: 40 mg (PO) on Days 1, 8, 15 and 22 (20 mg for pts ≥75 years of age). For D-Pd pts, DARA was given QW for C 1‑2, Q2W for C 3-6, and Q4W thereafter. Prior to protocol amendment, pts received DARA IV 16 mg/kg (n=7); after protocol amendment, all pts received DARA SC 1,800 mg co-formulated with recombinant human hyaluronidase PH20 (rHuPH20; ENHANZE^® drug delivery technology, Halozyme, Inc.). All pts were treated until disease progression or unacceptable toxicity. The primary endpoint was PFS. Major secondary endpoints included overall response rate, rates of very good partial response or better and complete response or better, MRD‑negativity rate, overall survival (OS), and safety.

Results

A total of 304 pts from 12 European countries were randomized (151 D-Pd; 153 Pd). The median (range) age was 67 (35-90) years, and 45%/33%/22% pts were ISS stage I/II/III. 35% had high cytogenetic risk (presence of del17p, t[14;16], or t[4;14]). 11% of pts had received 1PL (median [range] prior lines of therapy = 2 [1-5]). 79.6% of pts were refractory to len, 48.0% of pts were refractory to a PI, and 42.4% of pts were refractory to both. Median duration of treatment was 11.5 months with D-Pd vs 6.6 months with Pd.

The primary analysis was performed after 190 PFS events. The study met its primary endpoint of improved PFS; the hazard ratio (HR) was 0.63 (95% CI, 0.47-0.85; P=0.0018), representing a 37% reduction in the risk of progression or death in pts treated with D-Pd. The median PFS for the D-Pd vs Pd arms was 12.4 vs 6.9 months, respectively. With a median follow-up of 16.9 months, 99 pts (33%) have died; the HR for OS was 0.91 (95% CI, 0.61-1.35); survival data are immature and follow-up is ongoing. ≥CR rates for D-Pd vs Pd were 24.5% vs 3.9%; ≥VGPR rates were 51.0% vs 19.6%. The most common grade 3/4 adverse events with a >5% difference between D-Pd vs Pd were neutropenia (68% vs 51%), leukopenia (17% vs 5%), lymphopenia (12% vs 3%), febrile neutropenia (9% vs 3%), and pneumonia (13% vs 7%). The rate of IRRs with DARA SC was low (6%, all grade 1/2), and 2% of pts had local injection-site reactions (all grade 1). Median duration of injection was 5 mins. Rates of study treatment discontinuation due to TEAEs were similar for D-Pd vs Pd (2% vs 3%). The safety profile of D-Pd is consistent with known profiles of DARA SC and Pd.

Conclusion

In this phase 3 study evaluating DARA SC plus Pd, D-Pd significantly reduced the risk of progression or death by 37% in pts with RRMM who had received ≥1 prior line of therapy vs Pd alone. No new safety concerns were observed. The IRR rate was very low and administration duration short, thus increasing convenience for pts and decreasing treatment burden. Collectively, these data show that D-Pd is an effective and convenient treatment for pts with RRMM who received ≥1 prior therapy, including len and a PI.