2015 ASH Annual Meeting

Photo courtesy of ASH

ORLANDO, FL—A 3-drug regimen is likely not worth pursuing as a first-line treatment option for follicular lymphoma (FL), according to a presentation at the 2015 ASH Annual Meeting.

In a phase 1 study, combination ibrutinib, rituximab, and lenalidomide did not provide any response benefit over that previously observed with rituximab and lenalidomide.

But the triplet increased toxicity—particularly the incidence of rash—and necessitated dose modifications.

Chaitra S. Ujjani, MD, of Georgetown University Hospital in Washington, DC, presented these results at the meeting as abstract 471.*

“The combination of rituximab and lenalidomide has demonstrated remarkable activity in follicular lymphoma,” Dr Ujjani began.

She noted that, in the CALGB 50401 trial of relapsed FL (Leonard et al. JCO 2015), the combination elicited an overall response rate (ORR) of 76% and a complete response (CR) rate of 39%, and the 2-year time to progression was 52%.

In the CALGB 50803 trial of previously untreated FL (Martin et al. ASCO 2014, 8521), the regimen produced an ORR of 96%, a CR rate of 71%, and a 2-year progression-free survival (PFS) of 89%. In another trial of previously untreated FL (Fowler et al. Lanc Onc 2014), the ORR was 90%, the CR rate was 80%, and the 3-year PFS was 79%.

Ibrutinib has also demonstrated activity in FL, Dr Ujjani pointed out. In a phase 1 study of relapsed FL (Fowler et al. ASH 2012), the drug produced an ORR of 55%, 3 of 11 patients achieved a CR, and the median PFS was 13.4 months.

In a phase 2 study of ibrutinib in relapsed FL (Bartlett et al. ASH 2014, 800), the ORR was 30%, 1 of 40 patients achieved a CR, and the median PFS was 9.9 months.

With this in mind, Dr Ujjani and her colleagues conducted the A051103 trial to determine the activity and tolerability of rituximab, lenalidomide, and ibrutinib in previously untreated patients with FL.

Study design

The study enrolled patients with grade 1-3a FL; stage III, IV, or bulky stage II disease; an ECOG performance status less than 2; and adequate organ function.

They received 4 doses of rituximab at 375 mg/m² on days 1, 8, 15, and 22 of cycle 1 (28 days). They received 4 additional doses (375 mg/m²) on day 1 of cycles 4, 6, 8, and 10.

The patients received lenalidomide according to their assigned dosing cohort on days 1 to 21 for 18 cycles. They received daily ibrutinib according to their assigned dosing cohort until progression or unacceptable toxicity.

The study had a 3+3 dose-escalation design. Dose level (DL) 0 was lenalidomide at 15 mg and ibrutinib at 420 mg, DL1 was lenalidomide at 15 mg and ibrutinib at 560 mg, and DL2 was lenalidomide at 20 mg and ibrutinib at 560 mg.

Patients also received allopurinol at 300 mg daily for tumor lysis prophylaxis and aspirin as thromboprophylaxis while on lenalidomide.

The researchers assessed dose-limiting toxicities (DLTs) weekly during cycle 1. Given the known incidence of rash with lenalidomide, grade 3 rash that resolved to less than grade 2 within 10 days was not included as a DLT.

Once the maximum-tolerated dose was determined, there was a 10-patient expansion cohort.

Patients and treatment

Twenty-two patients were enrolled between June 2013 and May 2015. Their median age was 53.5 years (range, 36-81), and 68% were male.

Seventy-three percent of patients had grade 1/2 disease, and 77% had stage IV disease. By FLIPI, 18% of patients were low-risk, 55% were intermediate-risk, and 27% were high-risk.

Three patients were treated at DL0, 3 at DL1, and 16 at DL2. There were no DLTs reported at any dose level.

However, 11 patients required dose reductions due to toxicity (7 due to rash), and 12 patients ultimately discontinued treatment.

Reasons for discontinuation included progression (n=2), new diagnosis of carcinoma requiring systemic therapy (n=2), patient decision (n=3), and adverse events (n=6), including grade 3 rash (n=2), grade 3 atrial flutter (n=1), grade 3 diarrhea (n=1), hypertension (n=1), and depression (n=1). (One patient discontinued due to rash and progression.)

Adverse events

Dr Ujjani said the hematologic toxicity profile was similar to that observed with rituximab and lenalidomide in the front-line setting. Grade 3/4 hematologic toxicities included neutropenia (18.2%), thrombocytopenia (4.5%), anemia (4.5%), and lymphopenia (4.5%).

The most common non-hematologic toxicities (occurring in more than 20% of patients) were rash, diarrhea, fatigue, infusion-related reactions, nausea, infection, and neoplasms. There were no grade 4 non-hematologic toxicities.

Compared to rituximab and lenalidomide, the triplet was associated with an increase in rash, diarrhea, arthralgia, and neoplasm. There were 2 cutaneous neoplasms and 3 carcinomas.

Rash

“While no protocol-defined DLTs were observed, the regimen was associated with clinically significant rash,” Dr Ujjani noted. “Rash may have been related to individual study drugs or drug-drug interactions.”

Rash occurred in 82% of patients overall, 100% of patients treated at DL0, 67% at DL1, and 81% at DL2. The incidence of grade 1/2 rash was 46% overall, 67% at DL0, 33% at DL1, and 44% at DL2. The incidence of grade 3 rash was 36% overall, 33% at DL0 and DL1, and 38% at DL2.

The incidence of rash was similar whether or not patients received allopurinol. Ten of 11 patients on allopurinol had a rash, and 8 of 11 patients not on allopurinol had a rash.

“The time of [rash] onset was typically during cycle 1 but was seen as late as cycle 5,” Dr Ujjani said. “Grade 1 and 2 rashes resolved spontaneously without dose modification. The incidence of these milder rashes were comparable to our prior reports of rituximab and lenalidomide.”

“Grade 3 rash, however, occurred in 36% of patients, which is significantly higher than [with] rituximab and lenalidomide, [which is] typically 7% to 8%, or single-agent ibrutinib, which is about 3% to 4%.”

Patients with grade 3 rash were managed with supportive care, including acetaminophen, diphenhydramine, and oral corticosteroids.

All but 1 patient (7/8) had dose delays and reductions due to rash. One patient withdrew from the study because of rash, and 1 patient withdrew because of disease progression that occurred during a dose delay for rash.

Response and survival

The ORR was 95% for the entire cohort, 100% at DL0 and DL1 and 94% at DL2. The CR/unconfirmed CR rate was 63% overall, 67% at DL0, 33% at DL1, and 69% at DL2.

The partial response rate was 32% overall, 33% at DL0, 67% at DL1, and 25% at DL2. Five percent of patients had stable disease, all at DL2 (6% of this group).

The median time to first response was 2.3 months (range, 1.9 to 11.1). And the median time to best response was 5.5 months (range, 1.9 to 20.2).

At a median follow-up of 12.3 months, all patients are still alive. The 12-month PFS is 84%.

“Preliminary response data were similar to the prior CALGB/Alliance study of rituximab and lenalidomide,” Dr Ujjani noted. “However, given the increased toxicity and required dose modifications, the additional benefit of a third agent is not apparent, and further investigation of the triplet in this setting seems unwarranted.”

*Data in the abstract differ from data presented at the meeting.

Triplet disappoints in follicular lymphoma trial