Preclinical characterization of bemarituzumab, an anti-FGFR2b antibody for the treatment of cancer.

Bemarituzumab (FPA144) is a first-in-class, humanized, afucosylated immunoglobulin G1 monoclonal antibody (mAb) directed against fibroblast growth factor receptor 2b (FGFR2b) with two mechanisms of action against FGFR2b-overexpressing tumors: inhibition of FGFR2b signaling and enhanced antibody-dependent cell-mediated cytotoxicity (ADCC). Bemarituzumab is being developed as a cancer therapeutic, and we summarize here the key nonclinical data that supported moving it into clinical trials. Bemarituzumab displayed sub-nanomolar cross-species affinity for FGFR2b receptors, with >20-fold enhanced binding affinity to human Fc gamma receptor IIIa compared with the fucosylated version. In vitro, bemarituzumab induced potent ADCC against FGFR2b-expressing tumor cells, and inhibited FGFR2 phosphorylation and proliferation of SNU-16 gastric cancer cells in a concentration-dependent manner. In vivo, bemarituzumab inhibited tumor growth through inhibition of the FGFR2b pathway and/or ADCC in mouse models. Bemarituzumab demonstrated enhanced anti-tumor activity in combination with chemotherapy, and due to bemarituzumab-induced natural killer cell-dependent increase in programmed death-ligand 1, also resulted in enhanced anti-tumor activity when combined with an anti-programmed death-1 antibody. Repeat-dose toxicity studies established the highest non-severely-toxic dose at 1 and 100 mg/kg in rats and cynomolgus monkeys, respectively. In pharmacokinetic (PK) studies, bemarituzumab exposure increase was greater than dose-proportional, with the linear clearance in the expected dose range for a mAb. The PK data in cynomolgus monkeys were used to project bemarituzumab linear PK in humans, which were consistent with the observed human Phase 1 data. These key nonclinical studies facilitated the successful advancement of bemarituzumab into the clinic.

Blockade of nonhormonal fibroblast growth factors by FP-1039 inhibits growth of multiple types of cancer.

The fibroblast growth factor (FGF) pathway promotes tumor growth and angiogenesis in many solid tumors. Although there has long been interest in FGF pathway inhibitors, development has been complicated: An effective FGF inhibitor must block the activity of multiple mitogenic FGF ligands but must spare the metabolic hormone FGFs (FGF-19, FGF-21, and FGF-23) to avoid unacceptable toxicity. To achieve these design requirements, we engineered a soluble FGF receptor 1 Fc fusion protein, FP-1039. FP-1039 binds tightly to all of the mitogenic FGF ligands, inhibits FGF-stimulated cell proliferation in vitro, blocks FGF- and vascular endothelial growth factor (VEGF)-induced angiogenesis in vivo, and inhibits in vivo growth of a broad range of tumor types. FP-1039 antitumor response is positively correlated with RNA levels of FGF2, FGF18, FGFR1c, FGFR3c, and ETV4; models with genetic aberrations in the FGF pathway, including FGFR1-amplified lung cancer and FGFR2-mutated endometrial cancer, are particularly sensitive to FP-1039-mediated tumor inhibition. FP-1039 does not appreciably bind the hormonal FGFs, because these ligands require a cell surface co-receptor, klotho or ß-klotho, for high-affinity binding and signaling. Serum calcium and phosphate levels, which are regulated by FGF-23, are not altered by administration of FP-1039. By selectively blocking nonhormonal FGFs, FP-1039 treatment confers antitumor efficacy without the toxicities associated with other FGF pathway inhibitors.

rNAPc2 inhibits colorectal cancer in mice through tissue factor.

PURPOSE: Recombinant nematode anticoagulant protein c2 (rNAPc2) is a specific inhibitor of tissue factor (TF)/factor VIIa complex with novel antithrombotic activity. TF is highly expressed in human colorectal tumors, and levels are positively correlated with disease progression. EXPERIMENTAL DESIGN: To explore the therapeutic potential and mechanism of action of rNAPc2 during tumor growth and metastasis, we tested rNAPc2 in several experimental colorectal cancer models in mice. RESULTS: Administration of rNAPc2 inhibited pulmonary metastasis in mice systemically disseminated with CT26 murine colon carcinoma cells in a dose-dependent fashion. Combining rNAPc2 with the cytotoxic agent 5-fluorouracil or bevacizumab (humanized anti-vascular endothelial growth factor monoclonal antibody) resulted in additive growth inhibition and simultaneous reduction of microvessel density in HCT116 human colorectal tumor xenografts in nude mice. Furthermore, rNAPc2 potentiated CPT-11 in inhibiting hepatic metastasis in nude mice with portal vein injection of HCT116 tumor cells. Long-term administration of rNAPc2 significantly suppressed spontaneous formation of intestinal tumors in Apc(Min/+) mice. Using a RNA interference approach, we showed that TF expression is necessary for rNAPc2-mediated inhibition of HCT116 human colorectal tumor xenograft growth in nude mice, indicating that the antitumor effect of rNAPc2 may be transduced through TF that is expressed on tumor cells. CONCLUSIONS: rNAPc2 is a potent anticancer agent when used in combination with chemotherapy or antiangiogenic therapy in mouse models of colorectal cancer, and TF positivity appears to be required for its activity.

R-Spondin1 protects mice from chemotherapy or radiation-induced oral mucositis through the canonical Wnt/beta-catenin pathway.

R-Spondin1 (RSpo1) is a novel secreted protein that augments canonical Wnt/beta-catenin signaling. We injected recombinant RSpo1 protein into transgenic Wnt reporter TOPGAL mice and have identified the oral mucosa as a target tissue for RSpo1. Administration of RSpo1 into normal mice triggered nuclear translocation of beta-catenin and resulted in increased basal layer cellularity, thickened mucosa, and elevated epithelial cell proliferation in tongue. We herein evaluated the therapeutic potential of RSpo1 in treating chemotherapy or radiotherapy-induced oral mucositis in several mouse models. Prophylactic treatment with RSpo1 dose-dependently overcame the reduction of basal layer epithelial cellularity, mucosal thickness, and epithelial cell proliferation in tongues of mice exposed to whole-body irradiation. RSpo1 administration also substantially alleviated tongue mucositis in the oral cavity of mice receiving concomitant 5-fluorouracil and x-ray radiation. Furthermore, RSpo1 significantly reduced the extent of tongue ulceration in mice receiving a single fraction, high dose head-only radiation in a dose-dependent manner. Moreover, combined therapy of RSpo1 and keratinocyte growth factor resulted in complete healing of tongue ulcers in mice subjected to snout-only irradiation. In conclusion, our results demonstrate RSpo1 to be a potent therapeutic agent for oral mucositis by enhancing basal layer epithelial regeneration and accelerating mucosal repair through up-regulation of Wnt/beta-catenin pathway.

Mouse R-spondin2 is required for apical ectodermal ridge maintenance in the hindlimb.

The R-spondin (Rspo) family of proteins consists of secreted cysteine-rich proteins that can activate beta-catenin signaling via the Frizzled/LRP5/6 receptor complex. Here, we report that targeted inactivation of the mouse Rspo2 gene causes developmental limb defects, especially in the hindlimb. Although the initiation of the expression of apical ectodermal ridge (AER)-specific genes, including fibroblast growth factor 8 (FGF8) and FGF4 occurred normally, the maintenance of these marker expressions was significantly defective in the hindlimb of Rspo2(-/-) mice. Consistent with the ligand role of R-spondins in the Wnt/beta-catenin signaling pathway, expression of Axin2 and Sp8, targets for beta-catenin signaling, within AER was greatly reduced in Rspo2(-/-) embryos. Furthermore, sonic hedgehog (Shh) signaling within the hindlimbs of Rspo2(-/-) mice was also significantly decreased. Rspo2 is expressed in the AER of all limb buds, however the stunted phenotype is significantly more severe in the hindlimbs than the forelimbs and strongly biased to the left side. Our findings strongly suggest that Rspo2 expression in the AER is required for AER maintenance likely by regulating Wnt/beta-catenin signaling.

The lymphoid cell surface receptor NTB-A: a novel monoclonal antibody target for leukaemia and lymphoma therapeutics.

NTB-A is a CD2-related cell surface protein expressed primarily on lymphoid cells including B-lymphocytes from chronic lymphocytic leukaemia (CLL) and lymphoma patients. We have generated a series of monoclonal antibodies (mAbs) against NTB-A and assessed their therapeutic potential for CLL. Selective mAbs to NTB-A were further tested in functional complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicty (ADCC) assays in cell lines and B lymphocytes freshly isolated from CLL patients. While lower levels of NTB-A were detected in T and natural killer (NK) cells, CDC activity was demonstrated primarily in B cells isolated from CLL patients and B lymphoma cell lines. Knockdown of NTB-A by small interfering RNA in target cells results in lower cytotoxicity, demonstrating the specificity of the mAbs. Furthermore, anti NTB-A mAbs demonstrated anti-tumour activity against CA46 human lymphoma xenografts in nude mice and against systemically disseminated Raji human lymphoma cells in severe combined immunodeficient mice. Taken together, these results demonstrate NTB-A as a potential new target for immunotherapy of leukaemia and lymphomas.

R-spondin1, a novel intestinotrophic mitogen, ameliorates experimental colitis in mice.

BACKGROUND & AIMS: R-spondin 1 (Rspo1) is a novel epithelial mitogen that stimulates the growth of mucosa in both the small and large intestine. METHODS: We investigated the therapeutic potential of Rspo1 in ameliorating experimental colitis induced by dextran sulfate sodium (DSS) or trinitrobenzene sulfonic acid (TNBS) as well as nonsteroidal anti-inflammatory drug-induced colitis in interleukin (IL)-10-deficient mice. RESULTS: Therapeutic administration of recombinant Rspo1 protein reduced the loss of body weight, diarrhea, and rectal bleeding in a mouse model of acute or chronic DSS-induced colitis. Histologic evaluation revealed that Rspo1 improved mucosal integrity in both villus and/or crypt compartments in the small intestine and colon by stimulating crypt cell growth and mucosal regeneration in DSS-treated mice. Moreover, Rspo1 significantly reduced DSS-induced myeloperoxidase activity and inhibited the overproduction of proinflammatory cytokines, including tumor necrosis factor-alpha, IL-1alpha, IL-6, interferon-gamma, and granulocyte-macrophage colony-stimulating factor, in mouse intestinal tissue, indicating that Rspo1 may reduce DSS-induced inflammation by preserving the mucosal barrier function. Likewise, Rspo1 therapy also alleviated TNBS-induced interstitial inflammation and mucosal erosion in the mouse colon. Furthermore, Rspo1 substantially decreased the histopathologic severity of chronic enterocolitis by repairing crypt epithelium and simultaneously suppressing inflammatory infiltration in piroxicam-exposed IL-10(-/-) mice. Endogenous Rspo1 protein was localized to villus epithelium and crypt Paneth cells in mouse small intestine. CONCLUSIONS: Our results show that Rspo1 may be clinically useful in the therapeutic treatment of inflammatory bowel disease by stimulating crypt cell growth, accelerating mucosal regeneration, and restoring intestinal architecture.

The complete complement of C1q-domain-containing proteins in Homo sapiens.

The C-terminal domains of the A, B, C chains of C1q subcomponent of C1 complex represent a common structural motif, the C1q domain, that is found in a diverse range of proteins. We analyzed the human genome for the complete complement of this family and have identified a total of 31 independent gene sequences. The predominant organization of C1q-domain-containing (C1qDC) proteins includes a leading signal peptide, a collagen-like region of variable length, and a C-terminal C1q domain. There are 15 highly conserved residues within the C1q domain, among which 8 are invariant within the human gene set and these are predicted to cluster within the hydrophobic core of the protein. We suggest a 3-subfamily classification based on sequence homology. For some C1qDC-encoding genes, strict orthology has been retained throughout vertebrate evolution and these examples suggest a highly specific functional role for C1qDC proteins that has been under significant selective pressure. Alternatively, individual species have co-opted C1qDC proteins for roles that are highly specific to their biology, suggesting an evolutionary strategy of gene duplication and functional diversification. A more extensive analysis of the evolutionary relationship of C1qDC proteins reveals an ancient rooting, with clear members found in eubacterial species. Curiously, we have been unable to identify C1qDC-encoding genes in many eukaryotic genomcs, such as Sacchromyces cerivisae and C. elegans, suggesting that the retention or loss of this gene family throughout evolution has been sporadic.