Elevated folate receptor alpha (FRα) expression is characteristic of epithelial ovarian cancer (EOC), thus establishing this receptor as a candidate target for the development of novel therapeutics to treat this disease. Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate (ADC) that targets FRα for tumor-directed delivery of the maytansinoid DM4, a potent agent that induces mitotic arrest by suppressing microtubule dynamics. Here, combinations of IMGN853 with approved therapeutics were evaluated in preclinical models of EOC. Combinations of IMGN853 with carboplatin or doxorubicin resulted in synergistic antiproliferative effects in the IGROV-1 ovarian cancer cell line in vitro. IMGN853 potentiated the cytotoxic activity of carboplatin via growth arrest and augmented DNA damage; cell cycle perturbations were also observed in cells treated with the IMGN853/doxorubicin combination. These benefits translated into improved antitumor activity in patient-derived xenograft models in vivo in both the platinum-sensitive (IMGN853/carboplatin) and platinum-resistant (IMGN853/pegylated liposomal doxorubicin) settings. IMGN853 co-treatment also improved the in vivo efficacy of bevacizumab in platinum-resistant EOC models, with combination regimens causing significant regressions and complete responses in the majority of tumor-bearing mice. Histological analysis of OV-90 ovarian xenograft tumors revealed that concurrent administration of IMGN853 and bevacizumab caused rapid disruption of tumor microvasculature and extensive necrosis, underscoring the superior bioactivity profile of the combination regimen. Overall, these demonstrations of combinatorial benefit conferred by the addition of the first FRα-targeting ADC to established therapies provide a compelling framework for the potential application of IMGN853 in the treatment of patients with advanced ovarian cancer.

Over half of adults are seropositive for JC polyomavirus (JCV), but rare individuals develop progressive multifocal leukoencephalopathy (PML), a demyelinating JCV infection of the central nervous system. Previously, PML was primarily seen in immunosuppressed patients with AIDS or certain cancers, but it has recently emerged as a drug safety issue through its association with diverse immunomodulatory therapies. To better understand the relationship between the JCV life cycle and PML pathology, we studied autopsy brain tissue from a 70-year-old psoriasis patient on the integrin alpha-L inhibitor efalizumab following a ~2 month clinical course of PML. Sequence analysis of lesional brain tissue identified PML-associated viral mutations in regulatory (non-coding control region) DNA, capsid protein VP1, and the regulatory agnoprotein, as well as 9 novel mutations in capsid protein VP2, indicating rampant viral evolution. Nine samples, including three gross PML lesions and normal-appearing adjacent tissues, were characterized by histopathology and subject to quantitative genomic, proteomic, and molecular localization analyses. We observed a striking correlation between the spatial extent of demyelination, axonal destruction, and dispersion of JCV along white matter myelin sheath. Our observations in this case, as well as in a case of PML-like disease in an immunocompromised rhesus macaque, suggest that long-range spread of polyomavirus and axonal destruction in PML might involve extracellular association between virus and the white matter myelin sheath.

Purpose: c-Met dysregulation and/or overexpression are associated with tumor progression, metastasis and poor prognosis in numerous cancers. Despite strong pre-clinical evidence that blocking c-Met activity inhibits tumor cell growth and metastasis, targeted therapies have thus far failed to deliver an effective treatment option to the majority of patients. To address patients with both c-Met over-expressing and MET amplified tumors, we designed an antibody-drug conjugate (ADC) comprised of a humanized anti-c-Met monoclonal antibody linked to a highly potent indolinobenzodiazepine DNA-alkylating payload (DGN549) to enable activity against not only MET amplified but also c-Met over-expressing tumors. Experimental Design: Panels of monoclonal antibodies (Abs) against c-Met were generated and screened for antagonistic and agonistic activity in the presence or absence of the c-Met ligand, HGF. Lead Abs were humanized and conjugated to DGN549 either through lysine (Drug-to-Ab ratio (DAR) = 2.5) or engineered cysteine residues (DAR 2.0). Abs were also conjugated via lysine residues to the potent anti-microtubule maytansine derivative, DM4, using a sulfo-SPDB linker (DAR 3.5). Binding and cytotoxicity of ADCs were tested in vitro on normal and cancer cell lines with varying c-Met levels. Expression of c-Met was evaluated in patient tumors and xenografts along with normal human tissues using the CONFIRM immunohistochemistry assay. In vivo efficacy of anti-c-Met-DGN549 and anti-c-Met-DM4 ADCs was tested in both MET amplified and c-Met over-expressed (but non-amplified) xenograft tumor models. Results: A humanized anti-c-Met antibody, hucMet27, was identified which exhibits low c-Met agonist activity. Conjugates of hucMet27 were prepared with two different payloads, DGN549 and DM4, and in vitro and in vivo activity were determined. Both DGN549 and DM4 conjugates of hucMet27 bound with similar sub-nanomolar affinity to c-Met-expressing cells. hucMet27-DGN549 conjugates exhibited potent cytotoxicity against a large panel of c-Met expressing cell lines. By contrast, the potency of the hucMet27-DM4 conjugate was restricted mainly to cell lines harboring MET amplification, despite all cell lines demonstrating sensitivity to the unconjugated payload. When tested in mice bearing human xenograft tumors, both hucMet27-DGN549 and hucMet-DM4 conjugates were highly active in a MET amplified model, whereas hucMet27-DGN549 was more potent in inducing regressions in a model with c-Met over-expression without MET amplification. Conclusion: hucMet27-DGN549 exhibits compelling c-Met targeted anti-cancer activity in vitro and in vivo, and represents a promising therapeutic strategy to deliver a potent cytotoxic agent to tumor cells bearing a wide range of c-Met expression. Citation Format: Katharine C. Lai, Asli Muvaffak, Min Li, Marian Themeles, Surina Sikka, Kerry Donahue, Stuart W. Hicks, Angela Romanelli, Thomas Chittenden. In vitro and in vivo activity of a novel c-Met-targeting antibody-drug conjugate using a DNA-alkylating, indolinobenzodiazepine payload [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 45. doi:10.1158/1538-7445.AM2017-45

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A disintegrin and metalloprotease (ADAM) 9 is a member of the ADAM family of multifunctional, multidomain type 1 transmembrane proteins. ADAM9 is overexpressed in many cancers, including non-small cell lung, pancreatic, gastric, breast, ovarian, and colorectal cancer, but exhibits limited expression in normal tissues. A target-unbiased discovery platform based on intact tumor and progenitor cell immunizations, followed by an immunohistochemistry screen, led to the identification of anti-ADAM9 antibodies with selective tumor-versus-normal tissue binding. Subsequent analysis revealed anti-ADAM9 antibodies were efficiently internalized and processed by tumor cells making ADAM9 an attractive target for antibody-drug conjugate development. Here, we describe the preclinical evaluation of IMGC936, a novel antibody-drug conjugate targeted against ADAM9. IMGC936 is comprised of a high-affinity humanized antibody site-specifically conjugated to DM21-C, a next-generation linker-payload that combines a maytansinoid microtubule-disrupting payload with a stable tripeptide linker, at a drug antibody ratio of approximately 2.0. Additionally, the YTE mutation (M252Y/S254T/T256E) was introduced into the CH2 domain of the antibody Fc to maximize in vivo plasma half-life and exposure. IMGC936 exhibited cytotoxicity toward ADAM9-positive human tumor cell lines, as well as bystander killing, potent antitumor activity in human cell line-derived xenograft and patient-derived xenograft tumor models, and an acceptable safety profile in cynomolgus monkeys with favorable pharmacokinetic properties. Our preclinical data provide a strong scientific rationale for the further development of IMGC936 as a therapeutic candidate for the treatment of ADAM9-positive cancers. A first-in-human study of IMGC936 in patients with advanced solid tumors has been initiated (NCT04622774).