Vladimir Vainstein

Targeted Drug Delivery by Gemtuzumab Ozogamicin: Mechanism-Based Mathematical Model for Treatment Strategy Improvement and Therapy Individualization

Gemtuzumab ozogamicin (GO) is a chemotherapy-conjugated anti-CD33 monoclonal antibody effective in some patients with acute myeloid leukemia (AML). The optimal treatment schedule and optimal timing of GO administration relative to other agents remains unknown. Conventional pharmacokinetic analysis has been of limited insight for the schedule optimization. We developed a mechanism-based mathematical model and employed it to analyze the time-course of free and GO-bound CD33 molecules on the lekemic blasts in individual AML patients treated with GO. We calculated expected intravascular drug exposure (I-AUC) as a surrogate marker for the response to the drug. A high CD33 production rate and low drug efflux were the most important determinants of high I-AUC, characterizing patients with favorable pharmacokinetic profile and, hence, improved response. I-AUC was insensitive to other studied parameters within biologically relevant ranges, including internalization rate and dissociation constant. Our computations suggested that even moderate blast burden reduction prior to drug administration enables lowering of GO doses without significantly compromising intracellular drug exposure. These findings indicate that GO may optimally be used after cyto-reductive chemotherapy, rather than before, or concomitantly with it, and that GO efficacy can be maintained by dose reduction to 6 mg/m2 and a dosing interval of 7 days. Model predictions are validated by comparison with the results of EORTC-GIMEMA AML19 clinical trial, where two different GO schedules were administered. We suggest that incorporation of our results in clinical practice can serve identification of the subpopulation of elderly patients who can benefit most of the GO treatment and enable return of the currently suspended drug to clinic.

Recombinant interleukin-12, but not granulocyte-colony stimulating factor, improves survival in lethally irradiated nonhuman primates in the absence of supportive care: Evidence for the development of a frontline radiation medical countermeasure

Hematopoietic syndrome of acute radiation syndrome (HSARS) is a life‐threatening condition with no approved treatment. We compared recombinant human interleukin‐12 (rHuIL‐12; 175 ng/kg × 1) with vehicle, granulocyte‐colony‐stimulating factor (G‐CSF; 10 µg/kg/day × 18), or rHuIL‐12+G‐CSF after lethal irradiation in rhesus monkeys in a Good Laboratory Practice, randomized, blinded, placebo‐controlled study. Fluids, antibiotics, and blood products were not used. Survival at day 60 was significantly increased for rHuIL‐12 versus G‐CSF or vehicle. rHuIL‐12/G‐CSF combination provided no additional survival benefit over rHuIL‐12. Both rHuIL‐12 and rHuIL‐12+G‐CSF increased blood cell nadirs, induced earlier recovery of all hematopoietic lineages, and significantly decreased frequencies of severe cytopenias versus vehicle or G‐CSF. In bone marrow, rHuIL‐12 alone increased erythroid, myeloid, and megakaryocyte counts relative to vehicle or G‐CSF. Thus, a single injection of rHuIL‐12, without supportive medical intervention, significantly improved survival and promoted multilineage hematopoietic recovery in a nonhuman primate model of HSARS. Am. J. Hematol. 89:868–873, 2014.

Prediction of adverse events during intensive induction chemotherapy for acute myeloid leukemia or high‐grade myelodysplastic syndromes

Intensive chemotherapy for newly diagnosed acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) is associated with significant treatment‐related morbidity and mortality. Herein, we investigate how pretreatment characteristics relate to early adverse outcomes in such patients, studying 205 consecutive individuals receiving curative‐intent induction chemotherapy with cytarabine and an anthracycline (“7 + 3”; n = 175) or a “7 + 3”‐like regimen (n = 30). Among the entire cohort, baseline grade 4 neutropenia (i.e., absolute neutrophil count <500 cells/µL) was associated with development of fever (P = 0.04), documented infection (P < 0.0001), and bacteremia (P = 0.002) but not requirement for intensive care unit‐level care; after exclusion of the 30 patients who received “7 + 3”‐like induction, baseline grade 4 neutropenia remained associated with documented infection (P < 0.0001) and bacteremia (P = 0.0005). Among patients achieving a complete remission with the initial treatment cycle, grade 4 neutropenia was associated with delayed neutrophil count recovery (P < 0.0001). Low monocyte and lymphocyte counts at baseline were similarly associated with increased risk of documented infection or bacteremia. After adjustment for age, gender, disease type, cytogenetic/molecular risk, and performance status, the risk of fever, documented infection, or bacteremia was 1.87 (95% confidence interval: 1.04–3.34; P=0.04)‐fold, 4.95 (2.20–11.16; P<0.001)‐fold, and 3.14 (0.99–9.98; P=0.05)‐fold higher in patients with initial grade 4 neutropenia. Together, our studies identify severe baseline neutropenia as a risk factor for infection‐associated adverse events after induction chemotherapy and may provide the rationale for the risk‐adapted testing of myeloid growth factor support in this high‐risk AML/MDS patient subset. Am. J. Hematol. 89:423–428, 2014.

Analyzing transformation of myelodysplastic syndrome to secondary acute myeloid leukemia using a large patient database.

One‐third of patients with myelodysplastic syndrome (MDS) progress to secondary acute myeloid leukemia (sAML), with its concomitant poor prognosis. Recently, multiple mutations have been identified in association with MDS‐to‐sAMLtransition, but it is still unclear whether all these mutations are necessary for transformation. If multiple independent mutations are required for the transformation, sAML risk should increase with time from MDS diagnosis. In contrast, if a single critical biological event determines sAML transformation; its risk should be constant in time elapsing from MDS diagnosis. To elucidate this question, we studied a database of 1079 patients with MDS. We classified patients according to the International Prognostic Scoring System (IPSS), using either the French‐American‐British (FAB) or the World Health Organization (WHO) criteria, and statistically analyzed the resulting transformation risk curves of each group. The risk of transformation after MDS diagnosis remained constant in time within three out of four risk groups, and in all four risk groups, when patients were classified according to FAB or to the WHO‐determined criteria, respectively. Further subdivision by blast percentage or cytogenetics had no influence on this result. Our analysis suggests that a single random biological event leads to transformation to sAML, thus calling for the exclusion of time since MDS diagnosis from the clinical decision‐making process. Am. J. Hematol.

Integrating in vitro sensitivity and dose-response slope is predictive of clinical response to ABL kinase inhibitors in chronic myeloid leukemia.

BCR-ABL mutations result in clinical resistance to ABL tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). Although in vitro 50% inhibitory concentration (IC(50)) values for specific mutations have been suggested to guide TKI choice in the clinic, the quantitative relationship between IC(50) and clinical response has never been demonstrated. We used Hills equation for in vitro response of Ba/F3 cells transduced with various BCR-ABL mutants to determine IC(50) and the slope of the dose-response curve. We found that slope variability between mutants tracked with in vitro TKI resistance, provides particular additional interpretive value in cases where in vitro IC(50) and clinical response are disparate. Moreover, unlike IC(50) alone, higher inhibitory potential at peak concentration (IPP), which integrates IC(50), slope, and peak concentration (Cmax), correlated with improved complete cytogenetic response (CCyR) rates in CML patients treated with dasatinib. Our findings suggest a metric integrating in vitro and clinical data may provide an improved tool for BCR-ABL mutation-guided TKI selection.

Association of Hematological Nadirs and Survival in a Nonhuman Primate Model of Hematopoietic Syndrome of Acute Radiation Syndrome

Recombinant human interleukin-12 (rHuIL-12) mitigates the hematopoietic subsyndrome of acute radiation syndrome (HSARS) after total body irradiation (TBI) in a nonhuman primate (NHP) model of HSARS. The mechanism for this effect appears to involve multiple effects of rHuIL-12 on hematopoiesis. We conducted a meta-analysis to examine hematological nadirs and survival across our three NHP completed studies. Animals were irradiated (700 cGy) and treated with a single subcutaneous injection of vehicle (n = 64) or rHuIL-12 (50–500 ng/kg; n = 108) 24–25 h after irradiation, or with daily subcutaneous injections of granulocyte-colony stimulating factor (G-CSF; 10 μg/kg/day) for 18 days starting 24–25 h after exposure (n = 26). Blood samples were obtained at various time points up to day 60 after TBI. Lymphocytes, neutrophils and platelets were significantly lower in nonsurvivors than in survivors in the overall sample and in each treatment group (P < 0.001 for each comparison, Wilcoxon rank-sum test). Lymphocyte nadir was the strongest and most consistent predictor of death by Spearmans rank correlation. Receiver operating characteristic (ROC) curve analysis of death and threshold hematologic nadir values (where nadir values less than or equal the threshold are predictive of death) showed that a threshold of 0.08 × 109/L for lymphocytes had the largest positive predictive value of death (97.2% and 92.5% for the control and rHuIL-12 groups, respectively) and high sensitivity (76.1% and 62.7%, respectively), consistent with human radiation victims data. The current findings suggest that enhanced early bone marrow regeneration 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.

What's new in IL-12? Combination!

IL-12 is a heterodimeric, pro-inflammatory cytokine that enhances the cytotoxic activity of natural killer (NK) cells and cytotoxic CD8+ T-lymphocytes, and induces an IFN-α-dominated Th1 CD4+ T-lymphocyte response. IL-12 as an immunotherapeutic agent administered subcutaneously in cancer patients has demonstrated clinical responses in melanoma, T cell lymphoma, non-Hodgkins lymphoma, and AIDS-related Kaposi sarcoma, but was never developed further. Having elucidated novel hematological properties of IL-12, we are advancing our proprietary recombinant human IL-12 (NM-IL-12) for the treatment of the Hematopoietic Syndrome of Acute Radiation Syndrome. In three clinical safety studies conducted in over 200 healthy human volunteers, subcutaneous NM-IL-12 was well-tolerated. No adverse immune reactions or immunogenicity were observed. We have now developed a novel clinical paradigm for the use of subcutaneously administered, low dose NM-IL-12 combined with standard of care radiotherapy, chemotherapy, or immunotherapy for the treatment of cancer. The pleiotropic effects of IL-12 are expected to augment the mechanistic, anti-tumor effects of each of these treatments. In vitro NM-IL-12 stimulated primary human NK cell secretion of IFN-g and the cytotoxic lysis of leukemic cells, and inhibited production of pro-angiogenic IL-17 in human peripheral blood mononuclear cells. In vivo, recombinant murine IL-12 (rMuIL-12) caused significant tumor growth inhibition following total body irradiation (625cGy) in syngeneic Lewis lung and EL4 lymphoma tumor models. In the same models, rMuIL-12 in combination with cyclophosphamide also caused significant tumor growth inhibition. In the case of the non-immunogenic Lewis lung cancer model the combination of chemotherapy and IL-12 enhanced immunogenicity. In both tumor models, the antitumor effects of IL-12 were accompanied by rapid recovery of neutrophils, platelets and red blood cells, depressed by radiation or chemotherapy. This suggests an additional benefit of NM-IL-12 to cancer patients myelosuppressed following radiation or chemotherapy. Preclinical evaluation of NM-IL-12 with radiation therapy and chemotherapy is now followed by evaluating combination immunotherapy. PD-1 blockade elicits potent anti-tumor immunity in a subset of melanoma patients. We have thus evaluated the combination of rMuIL-12 and anti-PD-1 antibody in a clinically relevant, syngeneic model of spontaneous, highly metastatic B16 mouse melanoma has been tested. In summary we show that NM-IL-12 has excellent anti-tumor potential when used preclinically in combination with standard of care anti-cancer treatments, including radiation, chemotherapy and immunotherapy. NM-IL-12 is expected to contribute durable anti-tumor responses in the clinic through potent immunoactivation and anti-angiogenic effects, and to replenish blood cells, while being safe, well tolerated and non-immunogenic.