Efforts in redesigning the antileukemic drug 6-thiopurine: decreasing toxic side effects while maintaining efficacy

Construction and Biological Evaluation of Small Libraries Based on the Intermediates within the Total Synthesis of Uvaretin

Discovering therapeutic agents: New bioactive agents, either as sole or combinational agents, have been constructed through the synthetic manipulation of the intermediates within the total synthesis of the uvaretin class of natural products. It was found that increasing the hydrophobic character of the phenolic core correlates to a decrease in sole agent cytotoxicity. The synthesis of new, small chemical screening libraries (CSL) constructed from the intermediates of our total synthesis route of the uvaretin class of natural products is demonstrated herein. Numerous chalcone-based CSLs with various substitution on the phenolic groups within the chalcone core were assembled. Through cytotoxicity investigations, it was found that the level of hydrophobicity of the phenolic core of the chalcones gives biases: less cytotoxicity with more hydrophobic cores. In addition, it was observed that the potentiation, evaluated with 6-thiopurine in the pancreatic cancer cell line MIA PaCa-2, is tunable by the inclusion of less-hydrophobic character on the phenolic core. The role of the o-hydroxybenzyl group, present within the uvaretin family, was revealed to be cytotoxic in character. Merging all of the structure-activity relationship studies performed on the CSLs constructed in this effort led to the construction of a new chalcone hybrid possessing both a cytotoxic enone group and a small-molecule-potentiating, reduced enone group.

The winding road of the uvaretin class of natural products: from total synthesis to bioactive agent discovery

Herein, we disclose the development of a synthetic route to gain access to the uvaretin class of chalcone natural products. In this, the construction of a small library was achieved, and the collection was evaluated for cytotoxicity and other biological properties. Uvaretin (1) was accessed via a seven-step route in an overall yield of 15.1%. Within this route, the unsaturated enone variant of uvaretin (2), also a natural product, was accessed in a 16.7% yield over six steps. This route provides a nearly three-fold increase in yields of 1 and 2 in comparison to the previous synthetic route accessing them in 5.8% and 3.0% overall yields, respectively. Evaluation of 1 and 2 revealed IC₅₀ values between 2.0 and 5.1 μM in the cancerous cell lines HeLa, U937, A549, and MIA PaCa-2. Screening of the whole chalcone library set led to the discovery of over 30 compounds, within six cancerous cell lines, possessing single digit μM IC₅₀ activity as sole agents. Furthermore, multiple library members were found to possess promising potentiating properties with known chemotherapeutic agents.

New methods to assess 6-thiopurine toxicity and expanding its therapeutic application to pancreatic cancer via small molecule potentiators

6-Thiopurine (6TP) is a potent cytotoxic agent that is a clinically prescribed anti-metabolite employed in the treatment of numerous blood cancers since 1952. However, its reported severe toxicities limit its general usage in the clinic. We previously have undertaken investigations into identifying the mode of toxicity for 6TP, and have found that the oxidative metabolites of 6TP, specifically 6-thiouric acid (6TU), is responsible for the in vitro inhibition of UDP-glucose dehydrogenase (UDPGDH) in a UV-vis method. In this method, inhibition was quantified through the quantification of NADH production, however, purines absorb at the same wavelength and thereby can interfere with the NADH detection. Herein, we report a HPLC method that allows for direct quantification of UDP-glucuronic acid, product from UDPGDH, for the assessment of inhibition towards UDPGDH with no interference from purines. In this method it was revealed that 6TP possesses a greater inhibitory properties than previously observed; 111 vs. 288 μM. Building upon the data collected from a previously performed rat hepatocyte study, which correlated our in vitro to in vivo inhibition theories about UDPGDH, we have developed a bio-mimic in vitro assay to aid in the inhibitory assessment of 6TP and analogs. In our efforts to expand the use of 6TP, and analogs constructed, our laboratory has undertaken a screening campaign to identify small molecule potentiators that work in synergy with 6TP in other types of cancers. Three chalcone-based compounds have been discovered through our total synthesis campaign of uvaretin, and it has been found that 11c has strong synergism with 6TP in the pancreatic cancer cell line MIA PaCa-2. Through the work presented herein, we reveal new methods to assess toxicity of 6TP and future analogs and new small molecules that work in synergy to expand the therapeutic applications of this neglected cytotoxic agent.