Randomized Phase 2 Study of Weekly Carfilzomib 70 Mg/m2 and Dexamethasone Plus/Minus Cyclophosphamide in Relapsed and/or Refractory Multiple Myeloma (RRMM) Patients (GEM-KyCyDex)

Introduction:

Carfilzomib dosed at 56 mg/m² twice a week in combination with dexamethasone (Kd) is a standard of care for RRMM after 1-3 prior lines (PL) based on the ENDEAVOR study. Later, the ARROW study showed Kd dosed at 70 mg/m² weekly to be superior to Kd dosed at 27 mg/m² twice a week on RRMM patients (pts) after 2-3 PL. On the other side, Cyclophosphamide is an alkylating agent that has been widely combined with proteasome inhibitors and immunomodulatory drugs in MM, improving their efficacy with a good safety profile.

In this phase 2 randomized study, we have compared Kd plus cyclophosphamide (KCyd) with Kd in RRMM after 1-3PL, both with K dosed weekly at 70 mg/m².

Patients and methods:

RRMM after 1-3 PL of therapy were included in the trial. Consistently with the ENDEAVOR population, previous therapy with proteasome inhibitors was allowed but refractory patients were excluded.

Pts were randomized 1:1 to receive K at a dose of 70 mg/m² iv on days 1, 8 and 15 plus dexamethasone at a dose of 20 mg PO the day on and the day after K plus/minus KCyd at a dose of 300 mg/m² IV on days 1, 8 and 15 of each 28 days-cycle, as continuous treatment until progressive disease or unacceptable toxicity. The primary endpoint was PFS and key secondary endpoints included response rates, safety profile, and OS.

Results:

Between January 2018 and February 2020, 198 RRMM pts were included. 97 pts were randomized to KCyd and 101 to Kd. The baseline characteristics of the patients were well balanced between both groups. The median age was 70 years, and 70% and 28% of pts were older than 65 and 75. The median number of PL was one; 61% of pts had received 1 prior line. 94% and 92% of patients had been exposed to bortezomib in the KCyd and Kd and all of them were sensitive. 72% and 67% of patients had been exposed to IMiD's and 51% and 55% of them were IMiD's-refractory in the KCyd and Kd. Only 4 and 6 patients in KCyd and Kd, had received anti-CD38 antibodies being all refractory.

After a median f/u of 15.6 months, median PFS was 20.7 m and 15.2 m in KCyd and Kd (p=0.2). In pts after 1PL, median PFS has not been reached in any arm (p=0.4) and in patients after 2-3PL, KCyd resulted in a median PFS of 20.7 vs 11m for Kd (p=0.4). Of note, in the IMiD-refractory population, the addition of Cy to Kd resulted in a significant benefit in terms of PFS: 26.2 months vs 7.7 months in the Kd arm (p=0.01). OS is immature with 23 and 25 events so far in KCyd and Kd, respectively.

The ORR was 78% for KCyd and 73% for Kd: 20% of patients in both arms achieved at least complete response, 33% and 28% very good partial response, respectively, and 25% partial response in both arms. The MRD-ve rate was 4% and 5%.

As far as toxicity is concerned, neutropenia was the only hematological adverse event more frequently reported in KCyd compared with Kd, of any grade (24% vs 11%) and grade 3-4 (13% vs 7%). This did not translate into more infections and the rate was comparable in both arms (5% G3-4 in both arms). Thrombocytopenia of any grade and grade 3-4 occurred in 14%/1% and 18%/10% in KCyd/Kd. Cardiovascular events of any grade occurred in 22% and 30% of patients in KCyd and Kd. Nine pts in KCyd developed G3-4 cardiovascular events, these included atrial fibrillation (1pt), cardiac failure (2 pts), myocardial infarct (2 pts), and hypertension (4 pts). In the Kd arm, 11 patients developed G3-4 cardiovascular events and consisted of hypertension in most of them (9 pts).

Conclusion:

Cyclophosphamide added to Kd 70 mg/m2 weekly in RRMM pts after 1-3 PL prolonged the PFS as compared to Kd particularly in the lenalidomide-refractory population. The administration of K at a dose of 70 mg/m2 weekly was safe and more convenient and overall, the toxicity profile was manageable in both arms.