Phase I Study of Yttrium-90 Labeled ANTI-CD25 (aTac) Monoclonal Antibody PLUS BEAM for Autologous Hematopoietic Cell Transplantation (AHCT) in Patients with Mature T-Cell NON-Hodgkin Lymphoma, the "a-TAC-BEAM Regimen"

Background: Peripheral T cell lymphomas (PTCL) have a poor prognosis with current treatment regimens. High-dose chemotherapy followed by autologous stem cell transplant (ASCT) has been used as a consolidation strategy in remission states (CR1 or above) endorsed by the NCCN guidelines in appropriate patients. 5-year DFS is reported at 70% for alk -ve anaplastic large cell lymphoma (ALCL) and 30-40% for most other histologies (D'Amore et al, 2012, JCO). It is also performed in the relapsed settings if no previous ASCT performed and allogeneic transplant is not an option. CD25 is a targetable protein expressed differentially in PTCL and antibody based anti-CD25 therapies are efficacious in PTCL i.e denileukin diftitox (Foss et al Blood 2006, Dang et al, BJH 2006) , monoclonal antibody dacluzimab (Waldman et al 1995 Blood). Yttrium-90 (⁹⁰Y) labeled chimeric antiCD25 antibody basiliximab emits beta particles and has been shown to inhibit the growth of human ALCL tumors and increase survival in SUDHL-1 xenograft mice (Zhang et al 2009 Cancer Biother Radiopharm). Previous investigations at COH by Raubitschek, Colcher et al established a safe does of Yttrium-90 (⁹⁰Y) labeled basiliximab at 0.4mCi/kg in combination with BEAM. This is a phase 1 clinical trial of a novel conditioning regimen that includes the use of Yttrium-90 (⁹⁰Y) labeled basiliximab with BEAM chemotherapy for PTCL patients eligible for ASCT. The trial utilizes a modified version of the rolling 6 design (Skolnik et al) to test 3 dose levels of Yttrium-90 (⁹⁰Y) Basiliximab i.e 0.4mCi/kg, 0.5miC/kg and 0.6mCi/kg with the primary objective of evaluating the safety and tolerability of this combination and to establish the MTD. Secondary objectives include estimating incidence of relapse, OS, PFS, NRM at day 100, 1 year and 2 years post-transplant.

Patients and Methods: Dose limiting toxicity (DLT) is defined according to the Bearman and CTCAE 4.03 scales, the latter for hematologic toxicity. The study/treatment schema is shown in Figure 1.

Results: From 07/29/2015 to 06/10/2020, 20 patients underwent ASCT on this trial; n=4 at 0.4mCi/kg n=4 at 0.5mCi/kg and n=12 at 0.6mCi/kg. Median age at ASCT was 51 years (range: 18-76), and histologies included; PTCL-nos (n=10); alk-ve ALCL (n=5); angioimmunoblastic T-cell lymphoma (n=3); and intestinal T-cell lymphoma (n=2). Disease status at ASCT were CR1 in18, CR2 in 2 patients. Median number of prior therapies was 1 (range: 1-4). At a median follow-up of 17.1 months (range: 0.9-26.2), 12 patients remain in remission, 8 have relapsed out of which 5 have died of progressive lymphoma. OS was 100% (95% CI: N/A) at 100-days, and 83% (95% CI: 57-94) at 1 year. Non-relapse Mortality was 0% at both 100-days and 1-year. All patients successfully engrafted with the median days to ANC >= 500/ul was 10 (range: 10 - 21), and days to PLT >= 20,000/ul: 13 (12 - 92). Overall, no dose limiting toxicities were experienced. The most common/highest grade toxicity experienced (per Bearman Scale) was grade 2 stomatitis, which was seen in 3 patients at 0.4mCi/kg; 4 patients at 0.5 mCi/kg, and 7 at0.6mCi/kg. The only other toxicities seen were grade 2 GI in 2 patients at 0.4mCi/kg, and grade 2 bladder in one patient at 0.6mCi/kg dose.. Toxicities >grade 2 were not seen. Conclusion: aTac- BEAM appears to be safe as an ASCT conditioning regimen for PTCL with no increased toxicity as compared to the historical toxicities seen with BEAM alone in this patient population (D'Amore 2012 J of Clin Onc). The dose level 0.6mCi/kg will likely be the recommended phase II dose. An expanded phase is planned to evaluate the efficacy of this regimen followed by a randomized trial of BEAM alone plus a combination of aTac- BEAM.

Figure 1

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