A safety study of newly generated anti-podoplanin-neutralizing antibody in cynomolgus monkey ( Macaca fascicularis )

// Takao Ukaji 1 , Ai Takemoto 1 , Ryohei Katayama 1 , Kengo Takeuchi 2, 3 and Naoya Fujita 4 1 Division of Experimental Chemotherapy, The Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo, Japan 2 Division of Pathology, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan 3 Pathology Project for Molecular Targets, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan 4 The Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, Tokyo, Japan Correspondence to: Naoya Fujita, email: naoya.fujita@jfcr.or.jp Keywords: cynomolgus monkey (Macaca fascicularis); podoplanin; platelet aggregation; tumor metastasis; toxicity Received: April 06, 2018      Accepted: August 16, 2018      Published: September 07, 2018 ABSTRACT Hematogenous metastases are enhanced by platelet aggregation induced by tumor cell-platelet interaction. Podoplanin is a key molecule to enhance the platelet aggregation and interacts with C-type lectin-like receptor 2 (CLEC-2) on platelet via PLAG domains. Our previous reports have shown that blocking podoplanin binding to platelets by neutralizing antibody specific to PLAG4 domain strongly reduces hematogenous metastasis. However, podoplanin is expressed in a variety of normal tissues such as lymphatic vessels and the question remains whether treatment of tumors with anti-podoplanin neutralizing antibodies would be toxic. Monkeys are the most suitable species for that purpose. PLAG3 and PLAG4 domains had high homology among various monkey species and human. PLAG domain deleted mutants were indicated that monkey PLAG4 domain played a more crucial role in podoplanin-induced platelet aggregation than did the PLAG3 domain as in human. Moreover, newly established neutralizing antibodies (1F6, 2F7, and 3F4) targeting the monkey PLAG4 domain blocked interaction between monkey podoplanin and CLEC-2. Especially, the 2F7 neutralizing antibody strongly suppressed platelet aggregation and pulmonary metastasis. Furthermore, inhibiting podoplanin function with 2F7 neutralizing antibody exhibited no acute toxicity in cynomolgus monkeys. Our results suggested that targeting podoplanin with specific neutralizing antibodies may be an effective anticancer treatment.