MYTX-011: a pH-dependent anti-cMET antibody-drug conjugate designed for enhanced payload delivery to cMET expressing tumor cells.

Advances in linker payload technology and target selection have been at the forefront of recent improvements in antibody-drug conjugate (ADC) design, leading to several approvals over the last decade. In contrast, the potential of novel ADC technologies to enhance payload delivery to tumors is relatively underexplored. We demonstrate that incorporation of pH-dependent binding in the antibody component of a cMET targeting ADC (MYTX-011) can overcome the requirement for high cMET expression on tumors, an innovation that has the potential to benefit a broader population of patients with lower cMET levels. MYTX-011 drove four-fold higher net internalization than a non-pH engineered parent ADC in non-small cell lung cancer (NSCLC) cells and showed increased cytotoxicity against a panel of cell lines from various solid tumors. A single dose of MYTX-011 showed at least three-fold higher efficacy than a benchmark ADC in mouse xenograft models of NSCLC ranging from low to high cMET expression. Moreover, MYTX-011 showed improved pharmacokinetics over parent and benchmark ADCs. In a repeat dose toxicology study, MYTX-011 exhibited a toxicity profile similar to other MMAE-based ADCs. These results highlight the potential of MYTX-011 for treating a broader range of NSCLC patients with cMET expression than other cMET targeting ADCs. A first in human study is ongoing to determine the safety, tolerability, and preliminary efficacy of MYTX-011 in patients with NSCLC (NCT05652868).

MYTX-011: A pH-Dependent Anti-c-MET Antibody-Drug Conjugate Designed for Enhanced Payload Delivery to c-MET-Expressing Tumor Cells.

Advances in linker payload technology and target selection have been at the forefront of recent improvements in antibody-drug conjugate (ADC) design, leading to several approvals over the last decade. In contrast, the potential of novel ADC technologies to enhance payload delivery to tumors is relatively underexplored. We demonstrate that incorporation of pH-dependent binding in the antibody component of a c-mesenchymal-epithelial transition (MET)-targeting ADC (MYTX-011) can overcome the requirement for high c-MET expression on tumors, an innovation that has the potential to benefit a broader population of patients with lower c-MET levels. MYTX-011 drove fourfold higher net internalization than a non-pH-engineered parent ADC in non-small cell lung cancer (NSCLC) cells and showed increased cytotoxicity against a panel of cell lines from various solid tumors. A single dose of MYTX-011 showed at least threefold higher efficacy than a benchmark ADC in mouse xenograft models of NSCLC ranging from low to high c-MET expression. Moreover, MYTX-011 showed improved pharmacokinetics over parent and benchmark ADCs. In a repeat dose toxicology study, MYTX-011 exhibited a toxicity profile similar to other monomethyl auristatin E-based ADCs. These results highlight the potential of MYTX-011 for treating a broader range of patients with NSCLC with c-MET expression than other c-MET-targeting ADCs. A first-in-human study is ongoing to determine the safety, tolerability, and preliminary efficacy of MYTX-011 in patients with NSCLC (NCT05652868).

Bioactivation and toxicity of acetaminophen in a rat hepatocyte micropatterned coculture system.

We have recently shown that primary rat hepatocytes organized in micropatterned cocultures with murine embryonic fibroblasts (HepatoPac™) maintain high levels of liver functions for at least 4 weeks. In this study, rat HepatoPac was assessed for its utility to study chemical bioactivation and associated hepatocellular toxicity. Treatment of HepatoPac cultures with acetaminophen (APAP) over a range of concentrations (0-15 mM) was initiated at 1, 2, 3, or 4 weeks followed by the assessment of morphological and functional endpoints. Consistent and reproducible concentration-dependent effects on hepatocyte structure, viability, and basic functions were observed over the 4-week period, and were exacerbated by depleting glutathione using buthionine sulfoximine or inducing CYP3A using dexamethasone, presumably due to increased reactive metabolite-induced stress and adduct formation. In conclusion, the results from this study demonstrate that rat HepatoPac represents a structurally and functionally stable hepatic model system to assess the long-term effects of bioactivated compounds.

Long-term stability of primary rat hepatocytes in micropatterned cocultures.

Primary hepatocytes display functional and structural instability in standard monoculture systems. We have previously developed a model in which primary hepatocytes are organized in domains of empirically optimized dimensions and surrounded by murine embryonic fibroblasts (HepatoPac™). Here, we assess the long-term phenotype of freshly isolated and cryopreserved rat hepatocytes in a 96-well HepatoPac format. The viability, cell polarity (actin microfilaments, bile canaliculi), and functions (albumin, urea, Phase I/II enzymes, transporters) of fresh and cryopreserved rat hepatocytes were retained in HepatoPac at similar levels for at least 4 weeks as opposed to rapidly declining over 5 days in collagen/Matrigel™ sandwich cultures. Pulse or continuous exposure of rat HepatoPac to GW-7647, a selective agonist of PPARα, caused reproducible induction of CYP4A1 and 3-hydroxy-3-methylglutaryl-CoA synthase over 4 weeks. In conclusion, rat HepatoPac in a 96-well format can be used for chronic dosing of highly functional hepatocytes and assessment of perturbed hepatocellular pathways.

Parallel genome-scale loss of function screens in 216 cancer cell lines for the identification of context-specific genetic dependencies.

Using a genome-scale, lentivirally delivered shRNA library, we performed massively parallel pooled shRNA screens in 216 cancer cell lines to identify genes that are required for cell proliferation and/or viability. Cell line dependencies on 11,000 genes were interrogated by 5 shRNAs per gene. The proliferation effect of each shRNA in each cell line was assessed by transducing a population of 11M cells with one shRNA-virus per cell and determining the relative enrichment or depletion of each of the 54,000 shRNAs after 16 population doublings using Next Generation Sequencing. All the cell lines were screened using standardized conditions to best assess differential genetic dependencies across cell lines. When combined with genomic characterization of these cell lines, this dataset facilitates the linkage of genetic dependencies with specific cellular contexts (e.g., gene mutations or cell lineage). To enable such comparisons, we developed and provided a bioinformatics tool to identify linear and nonlinear correlations between these features.

Use of micropatterned cocultures to detect compounds that cause drug-induced liver injury in humans.

Because drug-induced liver injury (DILI) remains a major reason for late-stage drug attrition, predictive assays are needed that can be deployed throughout the drug discovery process. Clinical DILI can be predicted with a sensitivity of ~50% and a false positive (FP) rate of ~5% using 24-h cultures of sandwich-cultured primary human hepatocytes and imaging of four cell injury endpoints (Xu et al., 2008). We hypothesized that long-term drug dosing in a functionally stable model of primary hepatocytes (micropatterned cocultures [MPCCs]) could provide for increased predictivity over short-term dosing paradigms. We used MPCCs with either primary human or rat hepatocytes to understand possible species differences along with standard endpoints (glutathione levels, ATP levels, albumin, and urea secretion) to test 45 drugs either known or not known to cause clinical DILI. Human MPCCs correctly detected 23 of 35 compounds known to cause DILI (65.7% sensitivity), with a FP rate of 10% for the 10 negative compounds tested. Rat MPCCs correctly detected 17 of 35 DILI compounds (48.6% sensitivity) and had a higher FP rate than human MPCCs (20 vs. 10%). For an additional 19 drugs with the most DILI concern, human MPCCs displayed a sensitivity of 100% when at least two hepatocyte donors were used for testing. Furthermore, MPCCs were able to detect relative clinical toxicities of structural drug analogs. In conclusion, MPCCs showed superiority over conventional short-term cultures for predictions of clinical DILI, and human MPCCs were more predictive for human liabilities than their rat counterparts.