Akkinepally Raghuram Rao

Aromatase Inhibitors: A New Paradigm in Breast Cancer Treatment

Microsomal cytochrome P450 (CYP 450) enzyme aromatase belongs to CYP 19 super family. It is involved in the conversion of androgens to estrogens. In postmenopausal women the main sites of aromatisation are skin, adipose tissue and breast. Aromatase localized in breast tumor produces sufficient estrogen for its proliferation. Hence it is an important target for the treatment of hormone dependent breast cancer in postmenopausal women. There are mainly two types of aromatase inhibitors, one is steroidal another is nonsteroidal type. The first and second generation aromatase inhibitors encounter the undesirable drug- drug interactions besides being not very specific and plagued with pharmacokinetic problems. Third generation aromatase inhibitors developed recently are more potent and specific with a greater capacity to annihilate circulating estrogen levels. These agents have satisfactory pharmacokinetic profiles and are devoid of major drug-drug interactions. Third generation aromatase inhibitors became drugs of choice for both first and second line treatment of advanced breast cancer. Aromatase inhibitors can also be used for neoadjuvant therapy of breast cancer in which they have achieved better therapeutic efficacy than tamoxifen. Early results of ATAC (Armidex Tamoxifen Alone or Combination) trial suggest that anastrozole is superior to tamoxifen in adjuvant setting for disease free survival, particularly in receptor positive patients, and in reducing the incidence of contralateral breast cancer. Therapeutic potential of aromatase inhibitors stretches beyond the postmenopausal breast cancer treatment as they also play a role in the treatment of estrogen dependent benign and malignant conditions such as gynaecomastia, prostate cancer, fibroadenomata and the induction of ovulation. By virtue of their ability to reduce estrogen levels they pose problems like demineralization of bone, hot flushes and anti-implantation effects.

Anti-inflammatory potential of thienopyridines as possible alternative to NSAIDs.

The present study was designed to evaluate the anti-inflammatory and antiarthritic activity of the new synthetic thienopyridine analogs. The anti-inflammatory activity of thienopyridines was assayed by using carrageenan; dextran and arachidonic acid induced paw edema models (acute), cotton pellet granuloma model (Sub acute) and Freunds complete adjuvant induced arthritis (chronic) in experimental rats. The compounds BN-4, BN-14 and BN-16 have shown significant inhibition of edema in carrageenan and arachidonic acid induced paw edema model at a dose of 100mg/kg compared to the dextran induced paw edema model and also showed significant inhibition in granuloma tissue formation and Freunds complete adjuvant induced arthritis in experimental rats. These thienopyridine analogs also inhibited the proinflammatory mediators such as Tumor necrosis factor (TNF)-α, Interleukin (IL)-1β and Nitric Oxide (NO) in Lipopolysaccharide (LPS) challenged murine macrophages. Ulcerogenecity study results revealed less ulcerogenic potential of BN-4, BN-14 and BN-16 compared to nonsteroidal anti-inflammatory drug (NSAID) indomethacin in rats. In conclusion, the new thienopyridine analogs were promising for the potential use as anti-inflammatory agents for both acute and chronic inflammatory disorders with low toxic effects.

Molecular modeling evaluation of non-steroidal aromatase inhibitors.

A recent discovery of aromatase crystal structure triggered the efforts to design novel aromatase inhibitors for breast cancer therapy. While correlating docking scores with inhibitory potencies of known ligands, feeble robustness of scoring functions toward prediction was observed. This prompted us to develop new prediction models using stepwise regression analysis based on consensus of different docking and their scoring methods (gold, LigandFit, and glide). Quantitative structure–activity relationships were developed between the aromatase inhibitory activity (pIC50) of flavonoid derivatives (n = 39) and docking scores and docking descriptors. QSAR models have been validated internally [using leave‐one‐out cross‐validated )] and externally to ensure the predictive capacity of the models. Model 2 [M2] developed using consensus of docking scores of scoring functions viz. ASP, potential of mean force and DOCK Score ( = 0.850, r2 = 0.870,  = 0.633, RMSE = 0.363 μm, r2m(test) = 0.831, r2m(overall) = 0.832) was found to be better in predicting aromatase inhibitory potency (pIC50) compared to the Model 1 [M1] based on docking descriptors ( = 0.848, r2  =  0.825,  = 0.788, RMSE = 0.421 μm, r2m(test) = 0.808, r2m(overall) = 0.821). It has been observed that the natural flavonoids and their derivatives were less potent compared to these scaffolds with imidazolylmethyl substitution owing to the interaction of nitrogen atom of the imidazole ring toward the heme (Fe3+) of the aromatase. Results confirm the potential of our methodology for the design of new potent non‐steroidal aromatase inhibitors.

An improved synthesis of lysosomal activated mustard prodrug for tumor-specific activation and its cytotoxic evaluation

Cyclophosphamide, an alkylating agent widely used as anticancer agent, biotransformed in vivo to unstable phosphoramidic mustard and acrolein, where the latter metabolite has been found responsible for hemorrhagic cystitis and renal toxicity. Being one of the most popular strategies to avoid these deleterious effects, prodrug design has been attempted, which can, in addition, enable selective drug targeting. Our efforts to design, synthesize and evaluate the enzymatically activated prodrug phosphorodiamidic mustard as potential candidate for selective chemotherapy in antibody-directed enzyme prodrug therapy or prodrug monotherapy strategies are described. We propose an improved synthesis of prodrug 14, consisting of a galactose moiety, a spacer and a cytotoxic drug and its cytotoxicity has been investigated. The prodrug 14 has been found to be nontoxic (in vitro) which could be a valuable candidate for further development.