Antibody-Drug Conjugate PCMC1D3-Duocarmycin SA as a Novel Therapeutic Entity for Targeted Treatment of Cancers Aberrantly Expressing MET Receptor Tyrosine Kinase

Background: Aberrant expression of the MET receptor tyrosine kinase is an oncogenic determinant and a drug target for cancer therapy. Currently, antibody-based biotherapeutics targeting MET are under clinical trials. Objective: Here we report the preclinical and therapeutic evaluation of a novel anti-MET antibody-drug conjugate PCMC1D3-duocarmycin SA (PCMC1D3-DCM) for targeted cancer therapy. Methods: The monoclonal antibody PCMC1D3 (IgG1a/κ), generated by a hybridoma technique and specific to one of the MET extracellular domains, was selected based on its high specificity to human MET with a binding affinity of 1.60 nM. PCMC1D3 was conjugated to DCM via a cleavable valine-citrulline dipeptide linker to form an antibody-drug conjugate with a drug-to-antibody ratio of 3.6:1. PCMC1D3-DCM in vitro rapidly induced MET internalization with an internalization efficacy ranging from 6.5 to 17.2h dependent on individual cell lines. Results: Studies using different types of cancer cell lines showed that PCMC1D3-DCM disrupted cell cycle, reduced cell viability, and caused massive cell death within 96h after treatment initiation. The calculated IC50 values for cell viability reduction were 1.5 to 15.3 nM. Results from mouse xenograft tumor models demonstrated that PCMC1D3-DCM in a single dose injection at 10 mg/kg body weight effectively delayed xenograft tumor growth up to two weeks without signs of tumor regrowth. The calculated tumoristatic concentration, a minimal dose required to balance tumor growth and inhibition, was around 2 mg/kg bodyweight. Taken together, PCMC1D3-DCM was effective in targeting inhibition of tumor growth in xenograft models. Conclusion: This work provides the basis for the development of humanized PCMC1D3-DCM for MET-targeted cancer therapy in the future.

MAP4K4 determines cancer cell phenotype by controlling the plasma membrane-associated proteome

How the phenotype of Medulloblastoma (MB) tumor cells adapts in response to growth factor cues is poorly understood. We systematically determined alterations in the plasma membrane (PM)-associated proteome in growth factor-activated MB cells. We found that ligand-induced activation of c-MET receptor tyrosine kinase triggers specific internalization of c-MET and of membrane-associated and transmembrane proteins including nucleoside and ion transporters. In contrast, c-MET activation caused increased PM association of the PVR/CD155 adhesion and immunomodulatory receptor, promoting MB cell motility and tumor cell growth in the cerebellar tissue. Both increased and decreased PM association of a number of these proteins including PVR/CD155 is regulated by the Ser/Thr MAP4K4. We further identified Endophilin A proteins as potential regulators of this process downstream of MAP4K4 to contribute to HGF-induced invasion control. Together, our findings describe a novel link between MAP4K4 overexpression in MB and the maintenance of a cellular phenotype associated with growth and invasiveness.

Oncogenic mechanism-based pharmaceutical validation of therapeutics targeting MET receptor tyrosine kinase

Aberrant expression and/or activation of the MET receptor tyrosine kinase is characterized by genomic recombination, gene amplification, activating mutation, alternative exon-splicing, increased transcription, and their different combinations. These dysregulations serve as oncogenic determinants contributing to cancerous initiation, progression, malignancy, and stemness. Moreover, integration of the MET pathway into the cellular signaling network as an addiction mechanism for survival has made this receptor an attractive pharmaceutical target for oncological intervention. For the last 20 years, MET-targeting small-molecule kinase inhibitors (SMKIs), conventional therapeutic monoclonal antibodies (TMABs), and antibody-based biotherapeutics such as bispecific antibodies, antibody–drug conjugates (ADC), and dual-targeting ADCs have been under intensive investigation. Outcomes from preclinical studies and clinical trials are mixed with certain successes but also various setbacks. Due to the complex nature of MET dysregulation with multiple facets and underlying mechanisms, mechanism-based validation of MET-targeting therapeutics is crucial for the selection and validation of lead candidates for clinical trials. In this review, we discuss the importance of various types of mechanism-based pharmaceutical models in evaluation of different types of MET-targeting therapeutics. The advantages and disadvantages of these mechanism-based strategies for SMKIs, conventional TMABs, and antibody-based biotherapeutics are analyzed. The demand for establishing new strategies suitable for validating novel biotherapeutics is also discussed. The information summarized should provide a pharmaceutical guideline for selection and validation of MET-targeting therapeutics for clinical application in the future.

A minimal hepatocyte growth factor mimic acting as a powerful agonist of the MET receptor tyrosine kinase for regeneration of epithelial tissues and organs

Degenerative diseases of major internal epithelial organs such as liver, lung and kidney account for more than one third of mortality worldwide. The huge demand for drugs able to limit epithelial tissue degradation and eventually restore its functionality, place mimics of the hepatocyte growth factor/scatter factor (HGF/SF), the physiological ligand for the MET receptor tyrosine kinase, at the forefront of potential drug candidates. HGF/SF is a growth and motility factor with essential physiological roles in development and regeneration of epithelial organs. Unfortunately, HGF/SF itself is unsuitable for therapy because naturally the factor acts only locally as a morphogen and chemoattractant and has poor in vivo distribution and shelf life profile. We have therefore designed, produced, solved the crystal structure and characterized the biochemical and biological properties of K1K1, a new engineered fragment of HGF/SF for applications in tissue/organ regeneration. K1K1, a covalent dimer of the first kringle domain of HGF/SF, is recombinantly produced in bacterial cells, shows superior stability at physiological pH and ionic strength and is a potent receptor agonist as demonstrated in a wide range of biological assays with cells in culture and initial in vivo studies. K1K1 has broad potential in regenerative medicine with diseases such as acute liver failure, non-alcoholic steatohepatitis, chronic obstructive pulmonary disease and acute kidney injury.