‘Unprecedented’ efficacy for daratumumab in rel/ref MM

Efficacy

The “unprecedented” PFS, with a hazard ratio (HR) of 0.39 (95% CI, 0.28-0.53; P<0.0001), translated into a 61% reduction in the risk of disease progression or death for the experimental arm compared with the control arm.

The median PFS was not yet reached in the experimental arm, while the median PFS was 7.2 months in the control arm.

At 1 year, the PFS was 26.9% in the control arm and 60.7% in the experimental arm, “and this translates into a doubling in terms of remission duration for those patients,” Dr Palumbo stated.

“Even better was the outcome for the time to progression,” he said, with an HR of 0.30, “which means a 70% reduction in the risk of disease progression for DVd versus Vd, a more than doubling of time to disease progression.”

PFS by subgroup analysis showed that early intervention with daratumumab maximizes the efficacy of the combination.

For those patients who had received only 1 line of prior treatment, the HR was 0.31 (95% CI, 0.18 – 0.52; P<0.0001), which translated to a 69% reduction in the risk of progression or death for DVd compared with Vd.

The overall response rate revealed the profound cytoreduction achieved by the addition of daratumumab.

The CR rate increased from 9% in the control group to 19% in the experimental arm (P=0.0012), and the VGPR increased from 29% to 59%, in the control and experimental arms, respectively.

“So there is a doubling in the rate of CR and VGPR,” Dr Palumbo pointed out, “and this is quite relevant because more patients do achieve a profound cytoreduction.”

The rate of MRD negativity was 5 times higher for daratumumab-treated patients. Three percent of patients in the control arm were MRD negative (10^-4) compared with 14% in the experimental arm.

Time to response, “in my opinion, is an important issue because . . .  you can reach PR in around 1 month [with DVd] and this is clinically relevant because those patients are symptomatic,” he explained. “Reaching PR in 1 month means getting rid of pain in a quick way.”

“On the other hand, the achieving of CR requires a prolonged treatment,” he added. “CR is being achieved after 12 months of therapy, and MRD negativity might need even longer treatment.”

Safety

Daratumumab-treated patients experienced more thrombocytopenia and peripheral neuropathy (PN) of any grade than the control arm, 47% compared with 38%, respectively.

“But this is not due to the addition of the third agent,” Dr Palumbo clarified. “This is mainly the consequence, in the experimental arm, that treatment with bortezomib was longer in comparison to the control arm, and therefore, the typical toxicity of bortezomib—thrombocytopenia and PN—were slightly higher.”

There was also an increase in upper respiratory tract infections and cough in daratumumab-treated patients.

Grade 3-4 treatment-emergent adverse events occurring in more than 5% of patients included thrombocytopenia, anemia, neutropenia, lymphopenia, pneumonia, hypertension, and sensory PN.

However, grade 4 thrombocyotpenia, Dr Palumbo noted, did not translate into an increase in bleeding.

The major increase in toxicity due to daratumumab was in infusion-related reactions (IRRs), which occurred in 45% of patients. IRRs were consistent with the infusion of other monoclonal antibodies in cancer patients, he said, and 98% of patients with IRRs experienced them on the first infusion.

Conclusions

Dr Palumbo stressed that daratumumab did not increase the cumulative toxicity or the toxicity of the bortezomib-dexamethasone combination.

Daratumumab significantly improved PFS and the response rate; the experimental combination was associated with a 61% reduction in the risk of progression or death.