ANTITUMOR EFFECTS OF MONOCLONAL ANTIBODY FAB’FRAGMENT—CONTAINING IMMUNOCONJUGATES

Objective.Using monoclonal antibody (mAb) Fab′ fragment to develop mAb immunoconjugates for cancer. Methods.Fab′ fragment of mAb 3A5 was prepared by digestion of the antibody with pepsin and then reduced by dithiothreitol (DTT),while Fab′ fragment of mAb 3D6 was obtained by digestion of the antibody with ficin and subsequently reduced by β mercaptoethanol.The conjugation between Fab′ fragment and pingyangmycin (PYM),an antitumor antibiotic,was mediated by dextran T 40.Immunoreactivity of Fab′ PYM conjugates with cancer cells was determined by ELISA,and the cytotoxicity of those conjugates to cancer cells was determined by clonogenic assay.Antitumor effects of the Fab′ PYM conjugates were evaluated by subcutaneously transplanted tumors in mice. Results.The molecular weight of Fab′ fragment was approximately 53 kD,while the average molecular weight of Fab′ PYM conjugate was 170 kD.The Fab′ PYM conjugates showed immunoreactivity with antigen relevant cancer cells and selective cytotoxicity against target cells.Administered intravenously,Fab′ PYM conjugates were more effective against the growth of tumors in mice than free PYM and PYM conjugated with intact mAb. Conclusion.Fab′ PYM conjugate may be capable of targeting cancer cells and effectively inhibiting tumor growth,suggesting its therapeutic potential in cancer treatment.

Recent progress in the molecular imaging of therapeutic monoclonal antibodies

Therapeutic monoclonal antibodies have become one of the central components of the healthcare system and continuous efforts are made to bring innovative antibody therapeutics to patients in need.It is equally critical to acquire sufficient knowledge of their molecular structure and biological functions to ensure the efficacy and safety by incorporating new detection approaches since new challenges like individual differences and resistance are presented.Conventional techniques for determining antibody disposition including plasma drug concentration measurements using LC-MS or ELISA,and tissue distribution using immunohistochemistry and immunofluorescence are now complemented with molecular imaging modalities like positron emission tomography and near-infrared fluorescence imaging to obtain more dynamic information,while methods for characterization of antibody’s interaction with the target antigen as well as visualization of its cellular and intercellular behavior are still under development.Recent progress in detecting therapeutic antibodies,in particular,the development of methods suitable for illustrating the molecular dynamics,is described here.

Phase I Dose Escalation Study with the Lewis Y Carbohydrate Specific Humanized Antibody IGN311

Purpose: Investigation of safety, tolerability, pharmacokinetics, and anti-tumor activity of the Lewis Y-specific, fully humanized monoclonal antibody (mAb) IGN311 in patients with Lewis Y positive tumors in a Phase I clinical trial. Experimental Design: Twelve patients (pts) were enrolled in an open-label, uncontrolled, dose escalating Phase I study. Three pts received 50 mg, three pts 100 mg and six pts 200 mg IGN311 by i.v. infusion on days 1 and 15. Blood samples were taken immediately before infusion, and 0.5, 4, 8, 24 hours post infusion, as well as on days 3, 5 and 8 after the first and second infusion, respectively, and day 29. A final visit was scheduled for day 43. Results: No drug related adverse events were observed in the 50 mg and 100 mg dose groups. Three out of six patients in the 200 mg dose group showed drug related adverse reactions with nausea, vomiting and hypotension in one patient (NCI CTC grade 3) being the dose limiting toxicities. t1/2 of IGN311 was ~20 days after second infusion of IGN311. Sera of patients receiving IGN311 were capable of lysing Lewis Y positive tumor cells in vitro by both, complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Circulating tumor cells found in the peripheral blood in two out of twelve pts prior to treatment were reduced after treatment to below the quantification limit of the detection method. None of the patients showed an increase in the number of disseminated tumor cells during treatment period. Conclusions: The good safety and PK profile, the biological activity regarding CDC and ADCC mediated tumor cell lysis, and the elimination of circulating tumor cells warrant further clinical investigation of IGN311.

Mimotope peptide modified pompon mum-like magnetic microparticles for precise recognition,capture and biotransformation analysis of rituximab in biological fluids

Due to low immobilized ligand density,limited binding capacity,and severe interference from serum proteins,developing ideal peptide-based biomaterials for precise recognition and in vivo analysis of biopharmaceuticals remains a huge challenge.In this study,mimotope peptide modified pompon mum-like biomimetic magnetic microparticles(MMPs,3.8μm)that mimic the specific functionalities of CD20 on malignant B cells were developed for the first time.Benefit from the numerous ligand binding sites(Ni^(2+))on the pompon mum-like MMPs,these novel materials achieved≥10 times higher peptide ligand densities(>2300 mg/g)and antibody binding capacities(1380 mg/g)compared to previous reported biomaterials.Leveraging the high specificity of the mimotope peptide,rituximab can be precisely recognized and enriched from cell culture media or serum samples.We also established an LC-MS/MS method using the MMPs for tracking rituximab biotransformation in patient serum.Intriguingly,deamidation of Asn55 and Asn33,as well as oxidation of Met81 and Met34 were observed at the key complementarity determining regions of rituximab,which could potentially influence antibody function and require careful monitoring.Overall,these versatile biomimetic MMPs demonstrate superior recognition and enrichment capabilities for target antibodies,offering interesting possibilities for biotransformation analysis of biopharmaceuticals in patient serum.