Substance P (SP) is thought to play a cardinal role in emesis via the activation of central tachykinin NK 1 receptors during the delayed phase of vomiting produced by chemotherapeutics. Although the existing supportive evidence is significant, due to lack of an appropriate animal model, the evidence is indirect. As yet, no study has confirmed that emesis produced by SP or a selective NK 1 receptor agonist is sensitive to brain penetrating antagonists of either NK 1 , NK 2 , or NK 3 receptors. The goals of this investigation were to demonstrate: 1) whether intraperitoneal (i.p.) administration of either SP, a brain penetrating (GR73632) or non-penetrating (e.g. SarMet -SP) NK 1 receptor agonist, an NK 2 receptor agonist (GR64349), or an NK 3 receptor agonist (Pro 7 -NKB), would induce vomiting and/or scratching in the least shrew (Cryptotis parva) in a dose-dependent manner; and whether these effects are sensitive to the above selective receptor antagonists; 2) whether an exogenous emetic dose of SP (50 mg/kg, i.p.) can penetrate into the shrew brain stem and frontal cortex; 3) whether GR73632 (2.5 mg/kg, i.p.)-induced activation of NK 1 receptors increases Fos-measured neuronal activity in the neurons of both brain stem emetic nuclei and the enteric nervous system of the gut; and 4) whether selective ablation of peripheral NK 1 receptors can affect emesis produced by GR73632. The results clearly demonstrated that while SP produced vomiting only, GR73632 caused both emesis and scratching behavior dose-dependently in shrews, and these effects were sensitive to NK 1 -, but not NK 2 -or NK 3 -receptor antagonists. Neither the selective, non-penetrating NK 1 receptor agonists, nor the selective NK 2 -or NK 3 -receptor agonists, caused a significant dose-dependent behavioral effect. An emetic dose of SP selectively and rapidly penetrated the brain stem but not the frontal cortex. Systemic GR73632 increased Fos expression in the enteric nerve plexi, the medial subnucleus of nucleus tractus solitarius, and the dorsal motor nucleus of the vagus, but not the area postrema. Ablation of peripheral NK 1 receptors attenuated the ability of GR73632 to induce a maximal frequency of emesis and shifted its percent animals vomiting dose-response curve to the right. The NK 1 -ablated shrews exhibited scratching behavior after systemic GR73632-injection. These results, for the first time, affirm a cardinal role for central NK 1 receptors in SP-induced vomiting, and a Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. facilitatory role for gastrointestinal NK 1 receptors. In addition, the...

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CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody–drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent mono-methyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34+CD38− leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML.

SLITRK6 is a member of the SLITRK family of neuronal transmembrane proteins that was discovered as a bladder tumor antigen using suppressive subtractive hybridization. Extensive immunohistochemistry showed SLITRK6 to be expressed in multiple epithelial tumors, including bladder, lung, and breast cancer as well as in glioblastoma. To explore the possibility of using SLITRK6 as a target for an antibodydrug conjugate (ADC), we generated a panel of fully human mAbs specific for SLITRK6. ADCs showed potent in vitro and in vivo cytotoxic activity after conjugation to Monomethyl Auristatin E or Monomethyl Auristatin F. The most potent ADC, ASG-15ME, was selected as the development candidate and given the product name AGS15E. ASG-15ME is currently in phase I clinical trials for the treatment of metastatic urothelial cancer. This is the first report that SLITRK6 is a novel antigen in bladder cancer and also the first report of the development of ASG-15ME for the treatment of metastatic bladder cancer.

FLT3 (FMS-like tyrosine kinase 3) is a member of the class III receptor tyrosine kinase family, which is highly expressed in the blasts of both AML and ALL patients. In addition to FL ligand stimulation, FLT3 can also be activated by two distinct clusters of mutations: internal tandem duplications (FLT3/ITDs) in 20% to 25% patients and point mutations at position D835 in the tyrosine-kinase domain (FLT3/TKD) in 7% to 10% patients. FLT3 tyrosine kinase inhibitors (TKI) are mainly active against FLT3 mutant AML. An antibody drug conjugate (ADC), directed against the extracellular domain of FLT3 may only require FLT3 cell surface expression independent of mutation status. The restricted cellular distribution of FLT3 receptor and a higher expression in AML than in normal bone marrow makes FLT3 a favorable ADC target. Therefore, this ADC based strategy may offer a therapeutic alternative for AML patients independent of FLT3 status. Here, we report the preclinical assessment of a novel FLT3 targeting ADC, AGS62P1. AGS62P1 consists of a human anti-FLT3 monoclonal antibody, site specifically conjugated to a potent cytotoxic payload. FLT3 expression is confirmed in a large panel of AML and ALL tumor cells as well as in AML patient specimens via flow cytometry. The anti-leukemic activity of AGS62P1 was evaluated against AML and ALL tumor cell lines, in vitro and in vivo. AGS62P1 demonstrated strong binding affinity (0.1-0.5 nM) and potent cytotoxic activity in FLT3/ITD and Non-ITD tumor models, in vitro. Cytotoxic IC50 potency for AGS62P1 was 0.5-13 nM in FLT3/ITD and 0.2-12 nM in FLT3 non-ITD models. A fluorescence based assay confirmed that AGS62P1 is rapidly internalized in AML tumor cell lines. AGS62P1 is highly efficacious in FLT3/ITD and non-ITD tumor xenografts, leading to significant tumor growth inhibition or complete tumor regression. In primary AML patient xenograft drug treatment studies, the engraftment and outgrowth of 5/6 samples were significantly reduced when treated with AGS62P1. Taken together our data demonstrate that AGS62P1 exhibits potent antitumor activity against a broad panel of AML tumor models and primary AML samples, regardless of FLT3 status. We believe AGS62P1 may be an effective and alternative therapeutic for AML patients, which can bypass the TKI mediated resistance and deliver target specific effect through a different mode of action. Disclosures Jin: Agensys: Research Funding. Anand:Agensys: Employment. Dick:Agensys: Research Funding.