Distinct cellular and therapeutic effects of obatoclax in rituximab-sensitive and -resistant lymphomas.

Bcl-2 proteins represent a rheostat that controls cellular viability. Obatoclax, a BH3-mimetic, has been designed to specifically target and counteract anti-apoptotic Bcl-2 proteins. We evaluated the biological effects of obatoclax on the anti-tumour activity of rituximab and chemotherapy agents. Obatoclax induced cell death of rituximab/chemotherapy-sensitive (RSCL), -resistant cell lines (RRCL) and primary tumour-cells derived from patients with B-cell lymphomas (N=39). Obatoclax also enhanced the activity of rituximab and had synergistic activity when combined with chemotherapy agents. The ability of Obatoclax to induce PARP cleavage varied between patient samples and was not observed in some RRCL. Inhibition of caspase activity did not affect obatoclax activity, suggesting the existence of caspase-independent death pathways. Autophagy was detected by LC3 conversion and/or electron microscopy in RRCL and in patient-derived tumour cells. Moreover, obatoclax activity was inhibited by Beclin-1 knockdown. In summary, obatoclax is an active Bcl-2 inhibitor that potentiates the activity of chemotherapy agents and, to a lesser degree, rituximab. Defining the molecular events triggered by obatoclax is necessary to further its clinical development and identify potential biomarkers that are predictive of response.

Immunogenicity of antibody drug conjugates: bioanalytical methods and monitoring strategy for a novel therapeutic modality.

Immunogenicity (the development of an adaptive immune response reactive with a therapeutic) is a well-described but unwanted facet of biotherapeutic development. There are commonly applied procedures for immunogenicity risk assessment, testing strategies, and bioanalysis. With some modifications, these can be applied to new biotherapeutic modalities. For novel therapies such as antibody-drug conjugates (ADCs), the unique structural components may contribute additional complexities to both immunologic responses and bioanalytical methods. US product inserts (USPIs) for two commercially available ADCs detail the incidence of immunogenicity; however, the body of literature on immunogenicity of ADCs is limited. We recently participated in a conference session on this topic (Annual meeting of the American Association of Pharmaceutical Scientists, held November 2013 in San Antonio, TX, USA. The meeting featured the Symposium: Immunogenicity Assessment for Novel Antibody Drug Conjugates, Nonclinical to Clinical) which prompted an effort to share our perspectives on how immunogenicity risk assessment, testing strategies, and bioanalytical methods can be adapted to reflect the complexity of ADC therapeutics.

Bioavailability of everolimus administered as a single 5 mg tablet versus five 1 mg tablets: a randomized, open-label, two-way crossover study of healthy volunteers.

BACKGROUND: The mammalian target of rapamycin (mTOR) inhibitor everolimus has a well-established pharmacokinetics profile. We conducted a randomized, single-center, open-label, two-sequence, two-period crossover study of healthy volunteers to assess the relative bioavailability of everolimus administered as one 5 mg tablet or five 1 mg tablets. METHODS: Subjects were randomized 1:1 to receive everolimus dosed as one 5 mg tablet or as five 1 mg tablets on day 1, followed by a washout period on days 8-14 and then the opposite formulation on day 15. Blood sampling for pharmacokinetic evaluation was performed at prespecified time points, with 17 samples taken for each treatment period. Primary variables for evaluation of relative bioavailability were area under the concentration-time curve from time zero to infinity (AUCinf) and maximum blood concentration (Cmax). Safety was assessed by reporting the incidence of adverse events (AEs). RESULTS: Twenty-two participants received everolimus as one 5 mg tablet followed by five 1 mg tablets (n=11) or the opposite sequence (n=11). The Cmax of five 1 mg tablets was 48% higher than that of one 5 mg tablet (geometric mean ratio, 1.48; 90% confidence interval [CI], 1.35-1.62). AUCinf was similar (geometric mean ratio, 1.08; 90% CI, 1.02-1.16), as were the extent of absorption and the distribution and elimination kinetics. AEs, all grade 1 or 2, were observed in 54.5% of subjects. CONCLUSION: Although the extent of absorption was similar, the Cmax of five 1 mg tablets was higher than that of one 5 mg tablet, suggesting these formulations lead to different peak blood concentrations and are not interchangeable at the dose tested.

Conference report: hot topics in antibody-drug conjugate development.

American Association of Pharmaceutical Scientists National Biotechnology Conference Sheraton San Diego Hotel and Marina, San Diego, CA, USA, 19-23 May 2013 The National Biotechnology Conference, is a premier meeting for biotechnology professionals covering a broad range of hot topics in the biotechnology industry. Attracting participants from academia, industry and regulatory, this meeting features sessions that aim to address emerging subjects of interest and allows for open exchange between scientists. The 2013 conference featured leading researchers in the fields of antibody-drug conjugates (ADCs) and immunogenicity. Herein, we present a summary of the ADC hot topics, including bioanalytical and PK considerations, quantitative evaluation of the impact of immunogenicity and ADME to understand ADC drug-drug interactions, and clinical considerations for ADC development. This article aims to summarize the recommendations that were made by the speakers during various sessions throughout the conference.

American Association of Pharmaceutical Scientists National Biotechnology Conference Short Course: Translational Challenges in Developing Antibody-Drug Conjugates: May 24, 2012, San Diego, CA.

The American Association of Pharmaceutical Scientists (AAPS) National Biotechnology Conference Short Course "Translational Challenges in Developing Antibody-Drug Conjugates (ADCs)," held May 24, 2012 in San Diego, CA, was organized by members of the Pharmacokinetics, Pharmacodynamics and Drug Metabolism section of AAPS. Representatives from the pharmaceutical industry, regulatory authorities, and academia in the US and Europe attended this short course to discuss the translational challenges in ADC development and the importance of characterizing these molecules early in development to achieve therapeutic utility in patients. Other areas of discussion included selection of target antigens; characterization of absorption, distribution, metabolism, and excretion; assay development and hot topics like regulatory perspectives and the role of pharmacometrics in ADC development. MUC16-targeted ADCs were discussed to illustrate challenges in preclinical development; experiences with trastuzumab emtansine (T-DM1; Genentech) and the recently approved brentuximab vedotin (Adcetris; Seattle Genetics) were presented in depth to demonstrate considerations in clinical development. The views expressed in this report are those of the participants and do not necessarily represent those of their affiliations.

Synergism between clofarabine and decitabine through p53R2: a pharmacodynamic drug-drug interaction modeling.

Clofarabine (CLO), a purine nucleoside analog with promising efficacy in acute myeloid leukemia (AML), inhibits the ribonucleotidereductase, p53R2. We have shown that p53R2 mRNA is up-regulated by decitabine (DEC), another drug with promising activity in AML. We developed a pharmacodynamic model to characterize the interaction between CLO and DEC on an AML cell line and down-regulated p53R2 protein to understand its role. These results confirm a role for p53R2 in both CLO and DEC mechanism of action, demonstrate synergism between these two drugs in this AML model and support the use of this combination in a future clinical trial.