Harnessing the anti-cancer natural product nimbolide for targeted protein degradation

Nimbolide, a terpenoid natural product derived from the Neem tree, impairs cancer pathogenicity; however, the direct targets and mechanisms by which nimbolide exerts its effects are poorly understood. Here, we used activity-based protein profiling (ABPP) chemoproteomic platforms to discover that nimbolide reacts with a novel functional cysteine crucial for substrate recognition in the E3 ubiquitin ligase RNF114. Nimbolide impairs breast cancer cell proliferation in-part by disrupting RNF114 substrate recognition, leading to inhibition of ubiquitination and degradation of the tumor-suppressors such as p21, resulting in their rapid stabilization. We further demonstrate that nimbolide can be harnessed to recruit RNF114 as an E3 ligase in targeted protein degradation applications and show that synthetically simpler scaffolds are also capable of accessing this unique reactive site. Our study highlights the utility of ABPP platforms in uncovering unique druggable modalities accessed by natural products for cancer therapy and targeted protein degradation applications.

Antenatal care and skilled birth attendance in Bangladesh are influenced by female education and family affordability: BDHS 2014

OBJECTIVES

Antenatal care (ANC) during pregnancy and skilled birth attendance (SBA) during delivery are important policy concerns to reduce maternal deaths. Bangladesh is one of the developing countries which has made remarkable progress in both services during the last couple of decades by improving the SBA service rate from 16% in 2004 to 42.1% in 2014. However, this rate remains below the targeted level (50%) of the Health Population and Nutrition Sector Development Program set by the Ministry of the Health and Family Welfare of Bangladesh. This article explored the sociodemographic factors associated with the ANC and SBA service attainment. Furthermore, the possible implication of using ANC on SBA was also investigated.

STUDY DESIGN

The study followed a cross-sectional design using the Bangladesh demographic and health survey 2014, with a sample of size 4603 women with at least one live birth 3 years preceding the survey.

METHODS

Following a bivariate analysis, linear mixed-effect models were used to assess the relationship between sociodemographic factors and the outcome indicators (ANC and SBA). Finally, the association between SBA and ANC was evaluated through another mixed-effect model.

RESULTS

Wealth index, participation in household decisions, and partner's and respondent's education were significant predictors of ANC; whereas, residence, age at first birth, wealth index, working status, participation in household decisions, and partner and respondent's education were significant for SBA. Female education and household affordability were the strongest predictors for both ANC and SBA. ANC showed significant association with SBA as women accessing essential ANC during delivery seemed to be 4 times more likely (95% confidence interval: 3.05-5.93) to avail SBA services.

CONCLUSIONS

Overall, four factors were significant: residence, wealth index, education, and ANC access. Women residing in urban areas, having higher financial solvency, completing higher education, and accessing ANC by skilled personnel were more likely to receive SBA at delivery than their counterparts. Accessibility to skilled care during pregnancy leads to increased professional care during delivery. Thus, policies to encourage women and heads of families to seek skilled care during pregnancy would be beneficial to reach the maternal healthcare targets of Bangladesh.

Microscale screening of antibody libraries as maytansinoid antibody-drug conjugates

Antibody-drug conjugates (ADCs) are of great interest as targeted cancer therapeutics. Preparation of ADCs for early stage screening is constrained by purification and biochemical analysis techniques that necessitate burdensome quantities of antibody. Here we describe a method, developed for the maytansinoid class of ADCs, enabling parallel conjugation of antibodies in 96-well format. The method utilizes ∼ 100 µg of antibody per well and requires <5 µg of ADC for characterization. We demonstrate the capabilities of this system using model antibodies. We also provide multiple examples applying this method to early-stage screening of maytansinoid ADCs. The method can greatly increase the throughput with which candidate ADCs can be screened in cell-based assays, and may be more generally applicable to high-throughput preparation and screening of different types of protein conjugates.

Abstract 5442: Microscale methods for preparation and screening of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are hybrid biotherapeutics that combine the targeting specificity of monoclonal antibodies with chemically conjugated, highly potent small molecule chemotherapeutics. Using established research scale approaches, the amount of antibody material needed to prepare candidate ADCs far exceeds the quantities required for initial in vitro screening. The need to scale up production across many antibodies slows down early lead selection efforts and wastes material. We have therefore developed methods for conjugating multiple antibodies with ADC payloads in parallel at the 50-150 μg scale in 96-well plates. Pilot reactions show that antibodies can be titrated to different final drug:antibody ratios (DARs) with different payloads, and that differences in pH can alter the reaction kinetics with useful effects. We show that 96-well centrifugal ultrafiltration enables highly parallel ADC purification while maintaining the rigorous removal of residual cytotoxic impurities observed with more established methods such as gel filtration chromatography. In addition, we describe characterization of microscale ADCs using a single chromatographic assay requiring ∼5 μg of material. The resulting platform reduces the required input quantity of antibody required for in vitro ADC screening by at least 5-10 fold. It also enables much higher conjugation throughput with concomitant decrease in time needed to generate and characterize ADCs.

To assess the utility of the platform for ranking candidate antibodies, we compare in vitro cytotoxicity results for a panel of ADCs produced by both microscale and research scale methods. We also present three example screens in which antibody libraries of 10-85 members against different targets were conjugated using microscale methods and the resulting ADCs ranked by in vitro potency. For each antibody library, the screen size, conjugation conditions, and target DAR range were adjusted to suit the target biology, antibody type,and payload class. For example, we present evidence suggesting that, for targets in which functional antibody activity is not observed, normalization of DAR to the 2-6 range is adequate for screening. Across the screens, the success rates for producing ADC in quantity and quality suitable for screening were in the 75-90% range, using 200-600 μg of input antibody. Cytotoxic potencies ranging over 2-3 orders of magnitude were observed in the resulting ADC libraries, suggesting that microscale conjugation can rapidly focus ADC discoverycampaigns on high potency molecules.

For early stage antibody and ADC screening efforts, we find that microscale conjugation methods yield ADCs that can substitute for traditionally prepared conjugates. We expect these methods will be applicable across many different ADC targets and payloads, and possibly applicable more generally to conjugated macromolecule therapeutic or diagnostic reagents.

Citation Format: Nicholas C. Yoder, Kalli C. Catcott, Molly A. McShea, Carl Uli Bialucha, Parmita Saxena, Chen Bai, Kathy L. Miller, Thomas G. Gesner, Mikias Woldegiorgis, Stuart W. Hicks, Megan E. Lewis, Michael S. Fleming, Hans K. Erickson, Seth E. Ettenberg, Thomas A. Keating. Microscale methods for preparation and screening of antibody-drug conjugates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5442. doi:10.1158/1538-7445.AM2015-5442