Safety and Efficacy Data for Combined Checkpoint Inhibition with Ipilimumab (Ipi) and Nivolumab (Nivo) As Consolidation Following Autologous Stem Cell Transplantation (ASCT) for High-Risk Hematological Malignancies — CPIT-001 Trial

Rationale:

ASCT remains a standard-of-care as consolidation or salvage for multiple myeloma (MM), post-salvage consolidation for Diffuse Large B-Cell Lymphoma (DLBCL) and upfront consolidation or salvage for Peripheral T-Cell Lymphomas (PTCL) Pts with high-risk disease still show poor outcome and frequent progression within the first 18 months. Maintenance strategies post ASCT, particularly in lymphomas, have failed to show benefit, underlining the need for novel approaches to help disease control following ASCT. We have previously reported on the preliminary safety and efficacy of checkpoint inhibitor consolidation with Ipi and Nivo following ASCT trying to take advantage of the immunological milieu during post-ASCT recovery (Skarbnik et al., ASH 2017). Here we present updated data from our Phase I CPIT-001 trial.

Methods:

Pts with high-risk DLBCL, PTCL or MM (as defined in Table 1, divided in cohorts) were eligible if they experienced at least stable disease after most recent salvage therapy (NHL, PTCL or relapsed MM) or after induction therapy for high-risk MM.

Pts were enrolled prior to ASCT, starting in July 2016. All pts with DLBCL/PTCL received BEAM (carmustine 300 mg/m2 day -6, etoposide 200 mg/m2 and cytarabine 200 mg/m2 days -5 to -2, melphalan 140 mg/m2 day -1) as conditioning regimen for ASCT, all pts with MM received melphalan 200 mg/m2 on day -1

For pts who achieved appropriate hematologic recovery (ANC >800/mm3 and platelets > 20,000/mm3), Ipi/Nivo were started between days 14 and 28 post ASCT. The infusion schedule was:

• Ipi: 1 mg/kg; 6 doses Weeks 1, 4, 7, 10, 16, 22

• Nivo: 3 mg/kg; 12 doses Weeks 1, 4, 7, 10, 12, 14, 16, 18, 20, 22, 24, 26

Primary objectives were: Safety profile evaluation; PFS and OS at 18 months (PFS18 and OS18).

Cox proportional hazards regression was utilized to determine predictors of outcome.

Results:

31 pts received at least one dose of Ipi/Nivo following ASCT and were included in the intent-to-treat population. Median follow up for the whole cohort is 16 months. As of February 2018, the FDA has halted all studies including checkpoint inhibitors for pts with MM. At that time, only one pt with MM was actively receiving Ipi/Nivo, which was then discontinued.

At 18 months post ASCT, estimated PFS for the entire cohort was 67% and OS was 84% (Figures 1 and 2). Disease-specific PFS18 and OS18 are described in Table 2.

At study entry, 48% of pts were in CR (NHLs) or stringent CR (sCR, MMs). At most recent follow-up (range 2-25 months) 71% of pts were in CR (NHL) or sCR (MM). Disease status at study entry (i.e. CR vs <CR) didn't correlate with PFS nor OS.

65% of pts developed immune-related adverse events (irAEs) grade 2 or higher, requiring treatment with systemic steroids. Most common irAEs of any grade were: colitis (58%), rash (48%), thrombocytopenia (45%), anemia (45%) and transaminitis (32%). One pt (3%) died from complications of pneumonitis related to study drugs. All other irAEs resolved. Median time from 1^st Ipi/Nivo to development of irAEs was 4 weeks. Median time to improvement to Grade 1 or baseline was 1 week after high-dose steroids were initiated. Treatment-related AEs of any grade that led to discontinuation of Ipi/Nivo occurred in 6 pts (19%).

Development of irAEs, use of steroids or length of steroid-exposure did not correlate with PFS or OS.

Conclusion:

At 18 months post-ASCT, PFS for pts with high-risk hematological malignancies is 67%. This number underscores the potential for longer remissions by associating checkpoint inhibition with ASCT. For patients in the transplant-naïve MM with high-risk cytogenetics cohort, the 71% PFS18 (fig 3) is particularly striking, when compared to median PFS of 13-15 months in previous reports of ASCT alone in this patient population (Sonneveld et al, Blood 2016). In addition, the primary-refractory DLBCL population (43% of which were not in CR at time of ASCT) presented with a PFS18 of 83% (fig 4), while the reported PFS18 for this patient population with ASCT alone is 50% (Crump et al, Blood 2017). The cohort of pts with DLBCL relapsed within 1 year of induction had the poorest outcomes, possibly related to these pts being the most heavily pretreated in the whole cohort (median of 3 prior lines of therapy), with 57% of pts in this cohort refractory to most recent line of therapy.

The manageable toxicity profile, coupled with the encouraging efficacy outcomes warrant further evaluation of this approach in a Phase II trial, which is currently planned.

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