Use of tissue cross-reactivity studies in the development of antibody-based biopharmaceuticals: history, experience, methodology, and future directions.

Tissue cross-reactivity (TCR) studies are screening assays recommended for antibody and antibody-like molecules that contain a complementarity-determining region (CDR), primarily to identify off-target binding and, secondarily, to identify sites of on-target binding that were not previously identified. At the present time, TCR studies involve the ex vivo immunohistochemical (IHC) staining of a panel of frozen tissues from humans and animals, are conducted prior to dosing humans, and results are filed with the initial IND/CTA to support first-in-human clinical trials. In some cases, a robust TCR assay cannot be developed, and in these cases the lack of a TCR assay should not prevent a program from moving forward. The TCR assay by itself has variable correlation with toxicity or efficacy. Therefore, any findings of interest should be further evaluated and interpreted in the context of the overall pharmacology and safety assessment data package. TCR studies are generally not recommended for surrogate molecules or for comparability assessments in the context of manufacturing/cell line changes. Overall, the design, implementation, and interpretation of TCR studies should follow a case-by-case approach.

Distribution of RANK and RANK Ligand in Normal Human Tissues as Determined by an Optimized Immunohistochemical Method.

The expression and tissue distribution of RANK (Receptor Activator of Nuclear Factor κ B) and RANK Ligand (RANKL) are of critical interest in relation to efficacy and safety of antibodies against RANK or RANKL that are approved or under consideration as potential therapeutic agents. Data from the literature using protein or mRNA analyses of rodent and human tissues or immunohistochemical (IHC) studies with a variety of antibodies and methods have provided some background of the distribution of RANK and RANKL but have yielded inconsistent findings. The present study reports the generation of carefully validated antibodies to RANK and RANKL and the development of an optimized IHC method, with confirmatory data from 2 well-validated alternative protocols that were developed and performed in separate laboratories at USC and at Amgen. Tissue expression of RANK and RANKL is reported for the optimized IHC assay.

Interlaboratory validation of a CD71-based flow cytometric method (Microflow) for the scoring of micronucleated reticulocytes in mouse peripheral blood.

An interlaboratory study was performed to validate an anti-CD71/flow cytometry-based technique for enumerating micronucleated reticulocytes (MN-RETs) in mouse peripheral blood. These experiments were designed to address International Workshop on Genotoxicity Test Procedures validation criteria by evaluating the degree of correspondence between MN-RET measurements generated by flow cytometry (FCM) with those obtained using traditional microscopy-based methods. In addition to these cross-methods data, flow cytometric MN-RET measurements for each blood sample were performed at two separate sites in order to evaluate the reproducibility of data between laboratories. In these studies, groups of male CD-1 mice were treated with vehicle (saline or vegetable oil), a negative control (saline or vegetable oil), or four dose levels of five known genotoxicants (clastogens: cyclophosphamide, benzo[a]pyrene, 5-fluorouracil, methotrexate; aneugen: vincristine sulfate). Exposure occurred on 3 consecutive days via intraperitoneal injection, and blood samples were obtained approximately 24 hr after the final treatment. MN-RET frequencies were determined for each sample based on the analysis of 2,000 (microscopy) and 20,000 (FCM) reticulocytes. Regardless of the method utilized, each genotoxic agent was observed to cause statistically significant increases in the frequency of MN-RETs, and each response occurred in a dose-dependent manner. Spearman's correlation coefficient (rs) for FCM versus microscopy-based MN-RET measurements (nine experiments, 252 paired measurements) was 0.740, indicating a high degree of correspondence between methods. The rs value for all flow cytometric MN-RET measurements performed at the two independent sites was 0.857 (n = 248), suggesting that the automated method is highly transferable between laboratories. Additionally, the flow cytometric system offered advantages relative to microscopy-based scoring, including a greater number of cells analyzed, much faster analysis times, and a greater degree of objectivity. Collectively, data presented in this report suggest that the overall performance of mouse peripheral blood micronucleus tests is enhanced by the use of the flow cytometric scoring procedure.

A phase 2 randomized trial of paclitaxel and carboplatin with or without panitumumab for first-line treatment of advanced non-small-cell lung cancer.

INTRODUCTION: This two-part phase 2 study evaluated the efficacy and safety of panitumumab, a fully human anti-epidermal growth factor receptor monoclonal antibody, combined with carboplatin/paclitaxel in patients with previously untreated advanced non-small-cell lung cancer. METHODS: In part 1, patients were sequentially enrolled to receive paclitaxel 200 mg/m(2) and carboplatin (area under the concentration-versus-time curve, 6 mg/min/ml) plus panitumumab (1.0, 2.0, or 2.5 mg/kg). In part 2, patients were randomized 2:1 to receive paclitaxel/carboplatin with (arm A) or without (arm B) the maximum tolerated dose of panitumumab identified in part 1. Primary endpoints in parts 1 and 2 were the incidence of dose-limiting toxicities and time to progression (TTP), respectively. RESULTS: In part 1, four of 19 patients had dose-limiting toxicities: three at 2.0 mg/kg (fatigue, pain in extremity, dyspepsia) and one at 2.5 mg/kg (rash). The maximum tolerated dose was not reached; panitumumab 2.5 mg/kg was selected for part 2. In part 2, TTP was 18.1 weeks (95% confidence interval [CI], 13.6-23.3) in arm A and 23.0 weeks (95% CI, 15.9-24.1) in arm B (hazard ratio, 0.9; 90% CI, 0.66-1.21; p = 0.555). Progression-free survival in arms A and B was 17.6 weeks and 18.3 weeks, respectively, and the objective response rate was 15.2% and 11.1%. Adverse events occurring more frequently in arm A than in arm B included skin toxicity, diarrhea, stomatitis, vomiting, and dizziness. Exploratory analyses did not demonstrate associations between potential biomarkers and outcomes. CONCLUSION: Although toxicity was predictable and manageable, the addition of panitumumab to paclitaxel/carboplatin did not improve TTP in patients with previously untreated advanced non-small-cell lung cancer.

c-Met inhibitors with novel binding mode show activity against several hereditary papillary renal cell carcinoma-related mutations.

c-Met is a receptor tyrosine kinase often deregulated in human cancers, thus making it an attractive drug target. One mechanism by which c-Met deregulation leads to cancer is through gain-of-function mutations. Therefore, small molecules capable of targeting these mutations could offer therapeutic benefits for affected patients. SU11274 was recently described and reported to inhibit the activity of the wild-type and some mutant forms of c-Met, whereas other mutants are resistant to inhibition. We identified a novel series of c-Met small molecule inhibitors that are active against multiple mutants previously identified in hereditary papillary renal cell carcinoma patients. AM7 is active against wild-type c-Met as well as several mutants, inhibits c-Met-mediated signaling in MKN-45 and U-87 MG cells, and inhibits tumor growth in these two models grown as xenografts. The crystal structures of AM7 and SU11274 bound to unphosphorylated c-Met have been determined. The AM7 structure reveals a novel binding mode compared with other published c-Met inhibitors and SU11274. The molecule binds the kinase linker and then extends into a new hydrophobic binding site. This binding site is created by a significant movement of the C-helix and so represents an inactive conformation of the c-Met kinase. Thus, our results demonstrate that it is possible to identify and design inhibitors that will likely be active against mutants found in different cancers.