Treatment of human peripheral blood lymphocytes with cloned N alpha-desacetylthymosin alpha 1 induced interferon production. The kinetics is similar to that of mitogen-induced interferon induction. N alpha-desacetylthymosin alpha 1, in combination with mitogen, augments the amount of interferon produced. This interferon is immune interferon (IFN-gamma) as determined by sensitivity to pH 2, lack of neutralization by antibodies to IFN-alpha or IFN-beta and absence of activity of MDBK cells. Although the mechanism of induction of IFN-gamma by N alpha-desacetylthymosin alpha 1 is unclear, this compound is not mitogenic at concentrations causing IFN-gamma production. These results indicate that thymic factors may also participate in the regulation of IFN-gamma-production.

No abstract

Background: The prognosis for patients (pts) with relapsed T-ALL and T-LL is dismal; the primary goal of T-ALL/T-LL treatment is to prevent relapse. AALL1231 was a COG phase 3 clinical trial that randomized children and young adults (age 1-30 years) to a modified augmented BFM (aBFM) backbone +/- the proteasome inhibitor bortezomib during induction and delayed intensification (DI) (1.3mg/m2 x 4 doses per block). Bortezomib was tested in frontline therapy based on strong preclinical data and data in relapse on COG AALL07P1. Pts were stratified as standard (SR), intermediate (IR), or very high risk (VHR), primarily based on disease response: morphologic and minimal residual disease (MRD) at end induction and end consolidation (T-ALL) and radiographic response (T-LL). To eliminate cranial radiation (CXRT) in all pts, (except VHR: Day 29 M3 marrow or EOC MRD >0.1% or pts with overt CNS leukemia at diagnosis, CNS3), the aBFM backbone was modified to use dexamethasone (dex) as the sole corticosteroid and an extra pegaspargase dose was added in both induction and DI, following the MRC strategy. IR pts received a second interim maintenance (IM) phase (one Capizzi MTX; one HD-MTX). Following consolidation, VHR pts received 3 BFM high-risk intensification blocks in lieu of IM. Results: AALL1231 accrued 847 patients (824 eligible and evaluable) of 1400 anticipated from 2014 until early closure in 2017 when COG AALL0434 established that nelarabine (NEL) improved DFS in T-ALL (AALL1231 did not include NEL). The 3-year EFS for Arm A (no bortezomib) vs Arm B (bortezomib) were 81.7±2.4% and 85.1±2.2 % (HR=0.782, p=0.074) (3/31/20 data cut-off; see Table 1 for additional outcomes). SR and IR pts, who account for 95% of pts, had significantly improved EFS on Arm B as compared with Arm A. Yet, VHR patients had improved EFS on Arm A. Patients with T-LL had improved EFS and OS with bortezomib: 3-year EFS (76.5±5.9% vs 88.3±4.5%; p = 0.01); 3-year OS (78.0±5.8% vs 89.5±4.2%, p = 0.007). A similar improvement in EFS and OS was not seen in T-ALL; however, with longer follow-up this may change. No excess toxicity was seen on Arm B. A dex-based Induction did result in lower MRD rates; more T-ALL pts on AALL1231 had Day 29 MRD <0.1% as compared with AALL0434 which used a prednisone-based Induction (AALL1231 Arm A: 69.6%; Arm B: 72.2%; AALL0434: 64.6%; p = 0.02). However, this did not translate into improved survival. Indeed OS, but not EFS was worse on AALL1231 than AALL0434. On-going analyses are investigating the increased mortality on AALL1231, but preliminary analyses suggest a combination of increased toxic deaths and overall poor outcome in the VHR group. On AALL0434, 90.8% of T-ALL pts received CXRT. On AALL1231, 9.5% of subjects were scheduled to receive CXRT (CNS3 T-ALL/T-LL: 5.7%; VHR T-ALL: 4.1%). A comparison of AALL0434 pts that received CXRT with similar AALL1231 pts not receiving CXRT on AALL1231 demonstrated similar EFS (p = 0.14) and OS (p = 0.42) (Table 2). CNS relapse rates were higher in these pts on AALL1231 (4.5%) as compared with AALL0434 (1.7%), but overall relapse rates were the same (6.5% vs 6.4%). Notably the benefit of NEL in AALL0434 was due to reduction of CNS relapses. 128 AALL1231 pts came off protocol therapy after the study was closed for physician or patient/parent choice. Data collection is underway to understand the reasons for removal, including if it was to receive NEL. Conclusions: Outcomes for SR and IR pts with T-ALL and T-LL treated with bortezomib were excellent despite the elimination of prophylactic CXRT. Bortezomib significantly improved 3-year EFS for these groups, comprising ~95% of pts. Outcomes for VHR pts were dismal and worse on the bortezomib arm. T-LL pts had significantly improved EFS and OS with bortezomib on the AALL1231 backbone. This is the first trial to demonstrate an OS benefit for de novo pediatric T-LL with a new agent; however, longer follow-up is needed. Therapy intensification allowed elimination of CXRT in the majority of pts without excessive relapse. These results should be interpreted cautiously as the 3-yr OS on AALL1231 was inferior to AALL0434. Nevertheless, incorporating bortezomib into standard therapy for de novo T-LL appears advantageous. Future COG T-ALL/T-LLy trials will build on the positive findings from AALL0434 and AALL1231, balancing intensity while mitigating toxicity to maintain high cure rates without routine cranial radiation. (MLL, SPH, EAR contributed equally) Disclosures Teachey: Amgen: Consultancy; Janssen: Consultancy; La Roche: Consultancy; Sobi: Consultancy. Dunsmore:Dexcom: Current equity holder in publicly-traded company. Galardy:Abbott: Current equity holder in publicly-traded company; Abbvie: Current equity holder in publicly-traded company. Harker-Murray:Regerenon Pharmaceuticals: Consultancy. Hermiston:Sobi: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Shimano:Novartis: Research Funding; Daiichi Sankyo: Research Funding; Pfizer: Research Funding; Dova Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. McKay:Immunogen: Current Employment. Bollard:Mana Therapeutics: Other: IP. Loh:Medisix Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pfizer: Other: Institutional Research Funding. Hunger:Novartis: Consultancy; Amgen Inc.: Current equity holder in publicly-traded company, Honoraria. Raetz:Celgene/BMS: Other; Pfizer: Research Funding. OffLabel Disclosure: Bortezomib for the treatment of acute lymphoblastic leukemia under an IND

No abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive hematologic malignancy of plasmacytoid dendritic precursor cells. Lacking standard therapy due to limited understanding of biology and historical rarity of the disease, clinical outcomes for BPDCN patients remain poor. Surface overexpression of CD123/IL3Rα is seen 70-80% of patients with AML (Han et.al, Clin Cancer Res, 2017) and in nearly 100% of BPDCN cases, with a markedly high intensity compared to normal hematopoietic stem cells, thus making CD123 an attractive target for BPDCN treatment. IMGN632 is a CD123-targeting antibody-drug conjugate (ADC) comprised of a novel humanized anti-CD123 antibody G4723A linked to a DNA mono-alkylating payload of the indolindobenzodiazepine pseudodimer (IGN) class of cytotoxic compounds. IMGN632 demonstrates potent activity in AML samples at low concentrations with minimal impact on normal bone marrow progenitors, and anti-leukemia effects in AML xenograft models (Kovtun et.al., Blood Advances, 2018). A phase I clinical trial of IMGN632 in relapse/ refractory AML (NCT033865) is now being performed and achieved encouraging results. We thus explored the anti-tumor effect of IMGN632 in BPDCN. We first tested the in vitro activity of IMGN632 in a BPDCN cell line CAL-1. Cells were exposed to control antibody or IMGN632 at various concentration for 96 hours, after which viable cell numbers were measured using AnnexinV /DAPI assay with counting beads by flow cytometry. IMGN632 demonstrated cytotoxic activity at 0.2μg/ml, with stronger effects at concentrations of 2μg/ml and above (Figure 1A). Next, the in vivo efficacy of IMGN632 was evaluated in BPDCN patient-derived-xenograft (PDX) models. NSG mice (6-8 weeks old) were injected with 1e6/mouse BPDCN cells by tail vein 24 hours after 250cGY sublethal irradiation. Upon confirmation of the bone marrow engraftment of hCD45/hCD123 cells by bone marrow aspiration, mice were randomized to 5 or 8 mice/group and received weekly intravenous vehicle, control antibody or IMGN632 by tail vein injection 24 hours following FcR blockade (400mg/kg naked antibody by intraperitoneal injection) for 3 weeks. Bone marrow engraftment and survival were monitored. For model A, the mice received either 24μg/kg or 240μg/kg of IMGN632. For model B, the mice received 240μg/kg IMGN632. Both samples responded to the IMGN632 treatment, with the engraftment lower than 1% in the bone marrow after 3 doses, compared with over 90% in vehicle and control antibody group (Figure 1B). All mice from vehicle and control antibody groups in model A died by 52 days after cell injection; the 24μg/kg IMGN632 treated mice had prolonged survival with median survival of 111 days (p<0.0001), and the 240μg/kg IMGN632 treated mice are still alive after more than 140 days (p<0.0001) (Figure 1C). In the aggressive model B, a fraction of mice in each group died before efficacy could be established; the rest of the mice survived a median of 39 days in the control arm and 60 days in IMGN632-treated animals (p=0.0343) (Figure 1D). No evidence of treatment-related toxicity was observed using murine weight as a read-out. In summary, our preliminary data demonstrate pre-clinical proof of targeting CD123 in BPDCN using a novel antibody-drug conjugate. IMGN632 exhibited promising anti-tumor effects in BPDCN in vitro and in vivo, even at a dose 10-fold lower than the anticipated therapeutically active dose. This large therapeutic window would be expected to be advantageous when used in combination with other treatments in BPDCN. Disclosures Adams: ImmunoGen Inc.: Employment. Callum:ImmunoGen Inc.: Employment. Lane:Stemline Therapeutics: Research Funding; N-of-one: Consultancy. Kovtun:ImmunoGen Inc.: Employment. Daver:Daiichi-Sankyo: Research Funding; Novartis: Consultancy; Novartis: Research Funding; Incyte: Consultancy; BMS: Research Funding; Kiromic: Research Funding; Otsuka: Consultancy; Karyopharm: Consultancy; Alexion: Consultancy; Sunesis: Consultancy; Pfizer: Research Funding; Sunesis: Research Funding; Incyte: Research Funding; ARIAD: Research Funding; Pfizer: Consultancy; ImmunoGen: Consultancy; Karyopharm: Research Funding. Pemmaraju:Affymetrix: Research Funding; SagerStrong Foundation: Research Funding; plexxikon: Research Funding; daiichi sankyo: Research Funding; samus: Research Funding; celgene: Consultancy, Honoraria; abbvie: Research Funding; cellectis: Research Funding; stemline: Consultancy, Honoraria, Research Funding; novartis: Research Funding. McKay:ImmunoGen Inc.: Employment. Konopleva:Stemline Therapeutics: Research Funding.