Chris E. Lawrence

The impact of Fc engineering on an anti-CD19 antibody: increased Fcγ receptor affinity enhances B-cell clearing in nonhuman primates

CD19, a B cell-restricted receptor critical for B-cell development, is expressed in most B-cell malignancies. The Fc-engineered anti-CD19 antibody, XmAb5574, has enhanced Fcgamma receptor (FcgammaR) binding affinity, leading to improved FcgammaR-dependent effector cell functions and antitumor activity in murine xenografts compared with the non-Fc-engineered anti-CD19 IgG1 analog. Here, we use XmAb5574 and anti-CD19 IgG1 to further dissect effector cell functions in an immune system closely homologous to that of humans, the cynomolgus monkey. XmAb5574 infusion caused an immediate and dose-related B-cell depletion in the blood (to <10% of baseline levels) concomitant with a sustained reduction of natural killer (NK) cells. NK cells had fully recovered by day 15, whereas B-cell recovery was underway by day 57. B cells in secondary lymphoid tissues were depleted (to 34%-61% of vehicle), with involuted germinal centers apparent in the spleen. Anti-CD19 IgG1 had comparable serum exposure to XmAb5574 but demonstrated no B-cell depletion and no sustained NK-cell reduction. Thus, increasing FcgammaR binding affinity dramatically increased B-cell clearing. We propose that effector cell functions, possibly those involving NK cells, mediate XmAb5574 potency in cynomolgus monkeys, and that enhancing these mechanisms should advance the treatment of B-cell malignancies in humans.

CCR8 Is Not Essential for the Development of Inflammation in a Mouse Model of Allergic Airway Disease

Chemokine receptors play an important role in the trafficking of various immune cell types to sites of inflammation. Several chemokine receptors are differentially expressed in Th1 and Th2 effector populations. Th2 cells selectively express CCR3, CCR4, and CCR8, which could direct their trafficking to sites of allergic inflammation. Additionally, increased expression of the CCR8 ligand, TCA-3, has been detected in affected lungs in a mouse model of asthma. In this study, CCR8-deficient mice were generated to address the biological role of CCR8 in a model of allergic airway disease. Using two different protocols of allergen challenge, we demonstrate that absence of CCR8 does not affect the development of pulmonary eosinophilia and Th2 cytokine responses. In addition, administration of anti-TCA-3-neutralizing Ab during allergen sensitization and rechallenge failed to inhibit airway allergic inflammation. These results suggest that CCR8 does not play an essential role in the pathogenesis of inflammation in this mouse model of allergic airway disease.

Discovery of a potent and selective aurora kinase inhibitor.

This communication describes the discovery of a novel series of Aurora kinase inhibitors. Key SAR and critical binding elements are discussed. Some of the more advanced analogues potently inhibit cellular proliferation and induce phenotypes consistent with Aurora kinase inhibition. In particular, compound 21 (SNS-314) is a potent and selective Aurora kinase inhibitor that exhibits significant activity in pre-clinical in vivo tumor models.

Discovery of tetrahydroisoquinoline (THIQ) derivatives as potent and orally bioavailable LFA-1/ICAM-1 antagonists.

This letter describes the discovery of a novel series of tetrahydroisoquinoline (THIQ)-derived small molecules that potently inhibit both human T-cell migration and super-antigen induced T-cell activation through disruption of the binding of integrin LFA-1 to its receptor, ICAM-1. In addition to excellent in vitro potency, 6q shows good pharmacokinetic properties and its ethyl ester (6t) demonstrates good oral bioavailability in both mouse and rat. Either intravenous administration of 6q or oral administration of its ethyl ester (6t) produced a significant reduction of neutrophil migration in a thioglycollate-induced murine peritonitis model.

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.