maytansine and Colonic-Neoplasms

Topics: Adenocarcinoma; Adult; Aged; Clinical Trials as Topic; Colonic Neoplasms; Drug Evaluation; Female; Humans; Male; Maytansine; Middle Aged; Oxazines; Rectal Neoplasms

Maytansine and its related analogues are a class of highly potent anti-proliferation agents that have failed to be exploited as clinical drugs for human therapy due to unacceptable systemic toxicity. Here, we delineate a novel strategy that combines rational drug conjugation with subsequent nanoparticle assembly to systemically deliver this highly potent and toxic drug. To demonstrate this concept, we covalently coupled the thiolated maytansine derivative, the DM1 agent, to amphiphilic block co-polymers, polyethylene glycol (PEG)-block-polylactide (PLA), in varying molecular weights to generate two prodrug constructs (i.e., PEG

Topics: Animals; Antineoplastic Agents, Phytogenic; Chemistry, Pharmaceutical; Colonic Neoplasms; Drug Carriers; Drug Delivery Systems; Female; Humans; Male; Maytansine; Mice, Inbred BALB C; Mice, Inbred ICR; Mice, Nude; Nanoparticles; Polyesters; Polyethylene Glycols; Rats; Xenograft Model Antitumor Assays

In this report, we describe the synthesis of a panel of disulfide-linked huC242 (anti-CanAg) antibody maytansinoid conjugates (AMCs), which have varying levels of steric hindrance around the disulfide bond, in order to investigate the relationship between stability to reduction of the disulfide linker and antitumor activity of the conjugate in vivo. The conjugates were first tested for stability to reduction by dithiothreitol in vitro and for plasma stability in CD1 mice. It was found that the conjugates having the more sterically hindered disulfide linkages were more stable to reductive cleavage of the maytansinoid in both settings. When the panel of conjugates was tested for in vivo efficacy in two human colon cancer xenograft models in SCID mice, it was found that the conjugate with intermediate disulfide bond stability having two methyl groups on the maytansinoid side of the disulfide bond and no methyl groups on the linker side of the disulfide bond (huC242-SPDB-DM4) displayed the best efficacy. The ranking of in vivo efficacies of the conjugates was not predicted by their in vitro potencies, since all conjugates were highly active in vitro, including a huC242-SMCC-DM1 conjugate with a noncleavable linkage which showed only marginal activity in vivo. These data suggest that factors in addition to intrinsic conjugate potency and conjugate half-life in plasma influence the magnitude of antitumor activity observed for an AMC in vivo. We provide evidence that bystander killing of neighboring nontargeted tumor cells by diffusible cytotoxic metabolites produced from target cell processing of disulfide-linked antibody-maytansinoid conjugates may be one additional factor contributing to the activity of these conjugates in vivo.

Topics: Animals; Antibodies; Antineoplastic Agents; Carbon; Colonic Neoplasms; Disulfides; Humans; Maytansine; Mice; Mice, Inbred Strains; Mice, SCID; Molecular Conformation; Xenograft Model Antitumor Assays

Conjugation of cytotoxic compounds to antibodies that bind to cancer-specific antigens makes these drugs selective in killing cancer cells. However, many of the compounds used in such antibody-drug conjugates (ADC) are substrates for the multidrug transporter MDR1. To evade the MDR1-mediated resistance, we conjugated the highly cytotoxic maytansinoid DM1 to antibodies via the maleimidyl-based hydrophilic linker PEG(4)Mal. Following uptake into target cells, conjugates made with the PEG(4)Mal linker were processed to a cytotoxic metabolite that was retained by MDR1-expressing cells better than a metabolite of similar conjugates prepared with the nonpolar linker N-succinimidyl-4-(maleimidomethyl)cyclohexane-1-carboxylate (SMCC). In accord, PEG(4)Mal-linked conjugates were more potent in killing MDR1-expressing cells in culture. In addition, PEG(4)Mal-linked conjugates were markedly more effective in eradicating MDR1-expressing human xenograft tumors than SMCC-linked conjugates while being tolerated similarly, thus showing an improved therapeutic index. This study points the way to the development of ADCs that bypass multidrug resistance.

Topics: Adenocarcinoma; Animals; Antigens, Neoplasm; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Carcinoma, Renal Cell; Cell Adhesion Molecules; Cell Line, Tumor; Colonic Neoplasms; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Epithelial Cell Adhesion Molecule; Female; Humans; Immunotoxins; Kidney Neoplasms; Maleimides; Maytansine; Mice; Mice, SCID; Polyethylene Glycols

Conjugates of the anti-CanAg humanized monoclonal antibody huC242 with the microtubule-formation inhibitor DM1 (a maytansinoid), or with the DNA alkylator DC1 (a CC1065 analogue), have been evaluated for their ability to eradicate mixed cell populations formed from CanAg-positive and CanAg-negative cells in culture and in xenograft tumors in mice. We found that in culture, conjugates of either drug killed not only the target antigen-positive cells but also the neighboring antigen-negative cells. Furthermore, we showed that, in vivo, these conjugates were effective in eradicating tumors containing both antigen-positive and antigen-negative cells. The presence of antigen-positive cells was required for this killing of bystander cells. This target cell-activated killing of bystander cells was dependent on the nature of the linker between the antibody and the drug. Conjugates linked via a reducible disulfide bond were capable of exerting the bystander effect whereas equally potent conjugates linked via a nonreducible thioether bond were not. Our data offer a rationale for developing optimally constructed antibody-drug conjugates for treating tumors that express the target antigen either in a homogeneous or heterogeneous manner.

Topics: Animals; Antibodies, Monoclonal; Antigens, Neoplasm; Cell Line, Tumor; Colonic Neoplasms; Cross-Linking Reagents; Female; HT29 Cells; Humans; Immunoconjugates; Maytansine; Mice; Mice, SCID; Xenograft Model Antitumor Assays

Antibody-drug conjugates are targeted anticancer agents consisting of a cytotoxic drug covalently linked to a monoclonal antibody for tumor antigen-specific activity. Once bound to the target cell-surface antigen, the conjugate must be processed to release an active form of the drug, which can reach its intracellular target. Here, we used both biological and biochemical methods to better define this process for antibody-maytansinoid conjugates. In particular, we examined the metabolic fate in cells of huC242-maytansinoid conjugates containing either a disulfide linker (huC242-SPDB-DM4) or a thioether linker (huC242-SMCC-DM1). Using cell cycle analysis combined with lysosomal inhibitors, we showed that lysosomal processing is required for the activity of antibody-maytansinoid conjugates, irrespective of the linker. We also identified and characterized the released maytansinoid molecules from these conjugates, and measured their rate of release compared with the kinetics of cell cycle arrest. Both conjugates are efficiently degraded in lysosomes to yield metabolites consisting of the intact maytansinoid drug and linker attached to lysine. The lysine adduct is the sole metabolite from the thioether-linked conjugate. However, the lysine metabolite generated from the disulfide-linked conjugate is reduced and S-methylated to yield the lipophilic and potently cytotoxic metabolite, S-methyl-DM4. These findings provide insight into the mechanism of action of antibody-maytansinoid conjugates in general, and more specifically, identify a biochemical mechanism that may account for the significantly enhanced antitumor efficacy observed with disulfide-linked conjugates.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Cycle; Colonic Neoplasms; Cross-Linking Reagents; Disulfides; HT29 Cells; Humans; Immunotoxins; Lysosomes; Maytansine; Mice; Mice, SCID; Xenograft Model Antitumor Assays

C242-DM1 is a tumor-activated immunotoxin under development by GlaxoSmithKline plc (formerly SmithKline Beecham plc), under licence from ImmunoGen Inc, as a potential treatment for colon tumor. It consists of a colon cancer-specific humanized antibody, C242, conjugated to the maytansine derivative DM1. In preclinical studies, C242-DM1 caused complete tumor regression in animal models of both human pancreatic and non-small cell lung cancer (NSCLC) at non-toxic doses. C242-DM1 has also been evaluated in an immunoconjugate combination with J-591 (Cornell University). The J591-DM1 immunoconjugate demonstrated effective, antigen-specific delivery of a highly cytotoxic drug to PSMA-positive Pca cells in vitro and in vivo with low systemic toxicity. Results from studies in monkeys showed that C242-DM1 had no significant toxicity or side effects, when administered at doses higher than those that were previously shown to completely eradicate human colon tumors in mice [271420]. ImmunoGen acquired the right to evaluate, and an option to license, technology related to maytansines from Takeda. In February 1999, ImmunoGen and SmithKline Beecham signed a US $45 million development and commercialization agreement for C242-DM1 [313493]. In August 1997, Immunogen received an SBIR grant to advance development of huC242-DM1 [258356]. EP-00425235, held by ImmunoGen, covers conjugated forms of ansamitocin (maytansine) derivatives. Takeda holds several patents for the production of ansamitocin and its analogs, the first one being JP-53124692.

Topics: Animals; Antibodies, Monoclonal; Antineoplastic Agents, Phytogenic; Clinical Trials, Phase I as Topic; Colonic Neoplasms; Humans; Immunotoxins; Maytansine; Molecular Structure; Structure-Activity Relationship

Guided by cytotoxicity, ansamitocin P-3, a maytansinoid, was isolated in very low yield from two members of the moss family Thuidiaceae, Claopodium crispifolium (Hook.) Ren. & Card. and Anomodon attenuatus (Hedw.) Hueb. Ansamitocin P-3 showed potent cytotoxicity against the human solid tumor cell lines A-549, HT-29. A possible basis for the occurrence of this compound in mosses is discussed.

Topics: Actinomycetales; Antibiotics, Antineoplastic; Breast Neoplasms; Chromatography; Colonic Neoplasms; Humans; Lung Neoplasms; Magnetic Resonance Spectroscopy; Maytansine; Molecular Structure; Oxazines; Tumor Cells, Cultured

Topics: Acridines; Animals; Antimetabolites, Antineoplastic; Antineoplastic Agents; Aspartic Acid; Carcinoma; Cell Line; Colonic Neoplasms; Dose-Response Relationship, Drug; Drug Evaluation; Female; Humans; Lomustine; Male; Maytansine; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms, Experimental; Organophosphorus Compounds; Phosphonoacetic Acid; Streptozocin; Transplantation, Heterologous; Triazines