Calcineurin A versus NS5A-TP2/HD domain containing 2: a case study of site-directed low-frequency random mutagenesis for dissecting target specificity of peptide aptamers.

We previously identified a peptide aptamer (named R5G42) via functional selection for its capacity to slow cell proliferation. A yeast two-hybrid screen of human cDNA libraries, using R5G42 as "bait," allowed the identification of two binding proteins with very different functions: calcineurin A (CnA) (PP2B/PPP3CA), a protein phosphatase well characterized for its role in the immune response, and NS5A-TP2/HD domain containing 2, a much less studied protein induced subsequent to hepatitis C virus non-structural protein 5A expression in HepG2 hepatocellular carcinoma cells, with no known activity. Our objective in the present study was to dissect the dual target specificity of R5G42 in order to have tools with which to better characterize the actions of the peptide aptamers toward their individual targets. This was achieved through the selection of random mutants of the variable loop, derived from R5G42, evaluating their specificity toward CnA and NS5A-TP2 and analyzing their sequence. An interdisciplinary approach involving biomolecular computer simulations with integration of the sequence data and yeast two-hybrid binding phenotypes of these mutants yielded two structurally distinct conformers affording the potential molecular basis of the binding diversity of R5G42. Evaluation of the biological impact of CnA- versus NS5A-TP2-specific peptide aptamers indicated that although both contributed to the anti-proliferative effect of R5G42, CnA-binding was essential to stimulate the nuclear translocation of nuclear factor of activated T cells, indicative of the activation of endogenous CnA. By dissecting the target specificity of R5G42, we have generated novel tools with which to study each target individually. Apta-C8 is capable of directly activating CnA independent of binding to NS5A-TP2 and will be an important tool in studying the role of CnA activation in the regulation of different signaling pathways, whereas Apta-E1 will allow dissection of the function of NS5A-TP2, serving as an example of the usefulness of peptide aptamer technology for investigating signaling pathways.

Patient-reported outcomes validated in phase 3 clinical trials: a targeted literature review.

BACKGROUND: Regulatory guidance advises validation of patient-reported outcome (PRO) instruments prior to use in pivotal clinical studies, which may then be used to generate critical patient-centered evidence and support labelling claims. This targeted literature review aimed to determine if PRO instruments psychometrically validated in a phase 3 trial setting could support label claims from the same phase 3 study (i.e. PRO data were generated as an endpoint). METHODS: A targeted search of published studies (1 January 2006-3 June 2021) using the MEDLINE database identified PRO instruments validated during phase 3 trials. The search included instrument terms (e.g. patient-reported outcome measures, questionnaire, survey) and validation terms (e.g. reproducibility, minimal important difference), without filtering for therapeutic indications. Results were limited to phase 3 clinical trials or validation studies. The PROLABELS database was used to identify PROs validated in phase 3 trials and accepted in labelling claims. RESULTS: Of 355 references identified, 68 studies with PRO psychometric validation in phase 3 studies were selected, covering 78 instruments. Of these, 20 were novel PRO instruments and 58 were existing instruments being validated for a new therapeutic indication/population. The psychometric properties most frequently validated were internal consistency reliability, known-group validity, responsiveness, minimal important difference, and concurrent validity. Five novel instruments obtained ten labelling claims for seven drugs/products. CONCLUSIONS: These results suggest that quantitative validation of novel PRO instruments, and existing PROs for new indications, can occur within the context of phase 3 trials, and these PROs can also support label claims.

Enhanced Energetic State and Protection from Oxidative Stress in Human Myoblasts Overexpressing BMI1.

The Polycomb group gene BMI1 is essential for efficient muscle regeneration in a mouse model of Duchenne muscular dystrophy, and its enhanced expression in adult skeletal muscle satellite cells ameliorates the muscle strength in this model. Here, we show that the impact of mild BMI1 overexpression observed in mouse models is translatable to human cells. In human myoblasts, BMI1 overexpression increases mitochondrial activity, leading to an enhanced energetic state with increased ATP production and concomitant protection against DNA damage both in vitro and upon xenografting in a severe dystrophic mouse model. These preclinical data in mouse models and human cells provide a strong rationale for the development of pharmacological approaches to target BMI1-mediated mitochondrial regulation and protection from DNA damage to sustain the regenerative potential of the skeletal muscle in conditions of chronic muscle wasting.