BackgroundThe hematopoietic syndrome of the acute radiation syndrome (HSARS) is a life-threatening condition in humans exposed to total body irradiation (TBI); no drugs are approved for treating this condition. Recombinant human interleukin-12 (rHuIL-12) is being developed for HSARS mitigation under the FDA Animal Rule, where efficacy is proven in an appropriate animal model and safety is demonstrated in humans.MethodsIn this blinded study, rhesus monkeys (9 animals/sex/dose group) were randomized to receive a single subcutaneous injection of placebo (group 1) or rHuIL-12 at doses of 50, 100, 250, or 500 ng/kg (groups 2–5, respectively), without antibiotics, fluids or blood transfusions, 24–25 hours after TBI (700 cGy).ResultsSurvival rates at Day 60 were 11%, 33%, 39%, 39%, and 50% for groups 1–5, respectively (log rank p < 0.05 for each dose vs. control). rHuIL-12 also significantly reduced the incidences of severe neutropenia, severe thrombocytopenia, and sepsis (positive hemoculture). Additionally, bone marrow regeneration following TBI was significantly greater in monkeys treated with rHuIL-12 than in controls.ConclusionsData from this study demonstrate that a single injection of rHuIL-12 delivered one day after TBI can significantly increase survival and reduce radiation-induced hematopoietic toxicity and infections. These data significantly advance development of rHuIL-12 toward approval under the Animal Rule as an effective stand-alone medical countermeasure against the lethal effects of radiation exposure.

Multiple treatment modalities are available for MF, but most result in inevitable relapse. Therefore, new treatment strategies that improve response rate and prolong response duration are greatly needed. TSEBT is a highly effective therapy in MF. LD-TSEBT (12 Gy) is much more tolerable than the conventional 36+ Gy dose, thereby allowing for re-treatment; however, LD-TSEBT has a less favorable complete response rate and response duration. Combining LD-TSEBT with immunostimulatory modalities in MF has a strong biological rationale, since radiation-induced exposure of cancer-specific antigens should be synergistic with concomitant stimulation of anti-cancer immune responses. Interleukin-12 is a robust candidate for radioimmunotherapy, as IL-12 has significant anti-MF activity as monotherapy, is very well tolerated without overlapping toxicity with TSEBT, and is a potent stimulator of innate and adaptive immunity. We report on a single-arm open-label phase 2a trial of combination of LD-TSEBT and NM-IL-12. Ten patients are planned for enrollment. Eligibility includes MF-type CTCL stages IB-IIIB and patients must be eligible for LD-TSEBT. TSEBT is started on study day 1 (fractionated 4 Gy/week, up to 12 Gy). NM-IL-12 is administered subcutaneously at 150 ng/kg on days 2 and 15, followed by 6 maintenance doses q4w at 100 ng/kg. The primary endpoint is safety with secondary endpoints being response rate and PFS. Currently, 6 patients are enrolled, 5 evaluable for response; 4 male; median age 55; three have stage IB, one IIB and one IIIB. Median number of previous therapies is 2 (0-6). The treatment was well-tolerated with only grade 1 or 2 AEs; most common AEs include grade 1 headache and chills. One patient achieved CR, 2 PR, and 2 SD. Median follow-up is so far 15 weeks and 5 patients remain on study. One patient has been withdrawn from the study due to development of a suspected PLC (pityriasis lichenoides chronica)-like skin reaction requiring topical steroid therapy. PK and PD analysis was completed in the first 4 patients. It demonstrated measurable drug levels in all patients studied, Cmax being 10.8-56.1 pg/ml achieved at 5-24 hours post injection. Interferon-γ and IP-10 (hallmark PD markers of IL-12 activity) were measurable after the first and the second injections in all patients. Levels of the inhibitory cytokine IL-10 were generally measurable after NM-IL-12 injections, but were very low (<1 pg/ml up to 12 pg/ml) - much lower than previously reported in IL-12 studies, thus unlikely to be associated with negative immunosuppressive feedback. There was no clear correlation between PK and PD measurements and either efficacy or toxicity, but the number of patients fully evaluated is small. Total RNA was extracted from patient blood samples and subjected to qRT-PCR. Gene specific primers were used to analyse intracellular expression of the IL-12 receptor and immune cell markers. Ongoing work investigates an activated cellular phenotype at week 15 of LD-TSEBT and NM-IL-12 treatment compared with the respective baseline samples. Overall these early results demonstrate that NM-IL-12 can be safely administered together with LD-TSEBT in CTCL patients. Encouraging clinical activity is observed including a CR. Enrollment is currently ongoing and planned PD and correlative biomarker studies are in progress. A phase 2B randomized trial of NM-IL-12 and low dose TSEBT compared against low-dose TSEBT alone in patients with MF is being developed based on the apparent benign AE profile as compared to approved systemic therapies. Disclosures Kim: Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Eisai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tetralogic: Research Funding; Neumedicine: Research Funding; Merck: Research Funding; Kyowa Kirin Pharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Portola: Consultancy; miRagen: Research Funding; Innate: Research Funding; Horizon Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Soligenix: Research Funding. Ma:Neumedicines: Employment. Kha:Neumedicines: Employment. Lawrence:Neumedicines: Employment, Patents & Royalties. Vainstein:Neumedicines: Employment. Basile:Neumedicines: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Recombinant human interleukin-12 (rHuIL-12, HemaMaxTM) is being developed for mitigation of HSARS under the FDA Animal Rule using a NHP model of HSARS for proof of efficacy and clinical studies in healthy human subjects to demonstrate safety. We have shown previously that a single injection of rHuIL-12 administered 24-25 hours after lethal total body irradiaton (TBI), in the absence of antibiotics, fluids or blood products, resulted in improved survival while filgrastim (G-CSF) did not provide any survival benefit in our NHP HSARS model (Basile et al 2012, Gluzman-Poltorak et al 2014, Gluzman-Poltorak et al 2014). The mechanism by which IL-12 mitigates HSARS following TBI appears to involve multiple effects of IL-12 on hematopoieses. In our previous studies, animals treated with rHuIL-12 showed statistically significant reductions in the occurrence of severe neutropenia and severe thrombocytopenia, as well as attenuated nadirs for lymphocytes, neutrophils, platelets, and reticulocytes. To characterize further relationship between survival and hematological nadirs (lymphocytes, neutrophils, platelets, RBCs and reticulocytes) in the rhesus model of HSARS and to better understand the effects of rHuIL-12 versus G-CSF on blood cell nadirs, we undertook a meta-analysis analysis across three studies in irradiated rhesus monkeys. Animals used in this analysis were irradiated (700 cGy) and treated with a single subcutaneous injection of vehicle (n=64) or rHuIL-12 50-500ng/kg (n=108) 24-25 hours after irradiation, or daily subcutaneous injections of G-CSF at 10μg/kg/d for 18 days starting 24-25 hours after irradiation (n=26). Males and females were equal in each group. Lymphocytes, neutrophils and platelets were significantly lower in decedents versus monkeys that survived to day 60 overall and this was true in each treatment group (p<0.001, Wilcoxon rank-sum test). The mean RBC nadir was significantly higher in survivors compared to non-survivors in the rHuIL-12 group (p = 0.008), but not in the control group or the G-CSF group. Lymphocytes nadir appears to be the strongest and most consistent predictor of death followed by neutrophils and platelets (Spearman’s rank correlation). RBCs and reticulocytes are less informative in terms of predicting survival status. In addition, the receiver operating characteristic (ROC) curve area under the curve (AUC) by nadir value was assessed. The operating characteristics for lymphocytes, neutrophils and platelets allow for relatively large positive predictive values (PPV) of death with relatively high sensitivity. A cutoff value for lymphocytes nadir of 0.08x109/L (values less than or equal predicting death and higher values predicting life) allows for largest PPVs (97.2% and 92.5%) with 76.1% and 62.7% sensitivities for control and rHuIL-12 treatments, respectively. A cutoff value for neutrophils nadir of 0.03x109/L permits for 84% and 71.1% PPVs with sensitivities of 91.3% and 91.5 % for control and rHuIL-12 treatments, respectively. A cutoff value for platelets nadir of 9x109/L permits for 84.1% and 76.8% PPVs with sensitivities of 80.4% and 72.9 % for control and rHuIL-12 treatments, respectively. RBCs and reticulocytes were found less informative. To conclude, in the rhesus model of HSARS we have observed that an augmented hematological nadirs generally predicts an increased potential for survival as this effect reflects early bone marrow regeneration. The nadir for lymphocytes appears to be the strongest and most consistent predictor of death. Decrease of lymphocyte counts has been established as a best marker of bone marrow damage in a large database of human victims of acute radiation (METREPOL, Fliedner et al 2001). Thus, the correlation of our results with the human data supports the validity of our animal model as an accurate representation of human HSARS and its ability to predict effectiveness in humans exposed to lethal radiation. These data also suggest that the significant increase in early bone marrow regeneration seen in our studies, resulting in increases in nadir values for all major blood cell types, may be the main mechanism of action by which rHuIL-12 mitigates the lethality of HSARS. This project has been entirely funded with Federal funds from BARDA/ASPR/DHHS under Contract No. HHSO100201100037C. Disclosures Gluzman Poltorak: Neumedicines Inc.: Employment, Equity Ownership. Vladimir:Neumedicines Inc.: Consultancy, Employment, Equity Ownership. Basile:Neumedicines Inc.: Employment, Equity Ownership, Neumedicines Inc. Patents & Royalties.