Dr. Steve Fruchtman
Analyst
Thank you, Bruce, and good afternoon to everybody. On today's call, we will focus predominantly on our two most recent and exciting pieces of news. These relate to our newly announced plans to advance our lead assets narazaciclib into a Phase 1-2a trial in second and third line, low-grade endometrioid endometrial cancer and our recent presentation that the ESMO conference featuring updated data from investigator sponsored study of rigosertib. Our CMO, our Chief Medical Officer, Dr. Mark Gelder, who will go into more detail on each of these points, but I would first like to briefly outline the rationale, underlying the upcoming endometrial cancer trial, which will evaluate narazaciclib in combination with the non-steroidal aromatase inhibitor letrozole. Our decision to pursue this clinical program was driven by three key factors. First, we recognize that endometrial cancer, which arises in uterine lining is an indication with a pressing unmet medical need for improved therapies is a large, addressable patient population, and in fact is the most common cancer of the female reproductive organs, low-grade endometrioid endometrial cancer represents the target patient population for our newly announced clinical development program for narazaciclib. Second, we believe a clinical program evaluating narazaciclib in combination with letrozole in endometrial cancer as a high probability of technical and regulatory success. This belief is supported by clinical data that demonstrates the benefits of combining an agent that inhibits the CDK 4/6 pathway with letrozole in this indication. As a reminder, narazaciclib potently inhibits CDK 4/6 alongside additional tyrosine kinases that play important roles in cancer cell growth, survival and metastasis, clinical data, which Dr. Gelder will discuss in more detail substantially de-risks our upcoming trial by providing validation and clinical proof-of-concept for narazaciclib's mechanism of action in endometrial cancer. The third and last driving factor behind our decision to conduct our upcoming clinical trial was the opportunity to establish narazaciclib as a best-in-class therapy when combined with letrozole in recurrent endometrial cancer. While randomized Phase 2 studies established clinical proof-of-concept and compendium things, enable the off-label use and reimbursement of CDK 4/6 inhibitors such as palbociclib in this setting, these CDK 4/3 inhibitors on that FDA approved in endometrial cancer and have several short cuttings, related to safety, the tolerability and primary and acquired drug resistance. We believe narazaciclib can overcome these shortcomings, based on data that we have generated that Mark Gelder will, will highlight shortly. Lastly, before handing the call off to Mark to discuss our efforts in endometrial cancer and recent [indiscernible] data in more detail, I'll give a very quick update on the status of our trials. Starting with narazaciclib, I'm pleased to say that safety data from the ongoing Phase 1 solid tumor trials in both United States and China continue to be encouraging, with the maximum tolerated dose not yet reached in either study, both of which are in that 5th dose escalation cohort. These trials are valuate narazaciclib administered orally with two different schedules, varying the administration schemes of approved CDK 4/6 inhibitors, which represent multibillion dollar drug franchises although only approved an estrogen receptor positive and to negative metastatic breast cancer. Based on the encouraging safety funds to-date, we and our partner in China HanX biopharmaceuticals believe we may have the opportunity to dose escalate further in each trial, leaving us better positioned to drive efficacy in subsequent studies. Accounting for the expected addition of dose escalation cohorts, we now anticipate identifying a recommended Phase 2 dose in the first half of 2023. We anticipate the dose administration scheme for narazaciclib in our Phase 1 plus 2a study and our other studies being planned will be once daily continuous dosing of narazaciclib. I want to point out that a two out of three approved CDK 4/6 inhibitors are dosed in a three week on and one week off scheme. This one week off requirements potentially permits the tumor cells to proliferate during this week versus continuous suppression of the cancer that daily dosing may provide. The other CDK 4/6 agent is typically dosed daily, but due to its half life requires twice daily dosing. It appears that narazaciclib will be dosed once daily and continuously. Looking forward, we remain interested in several indications, but narazaciclib development beyond endometrial cancer, as discussed on past earnings calls. While it's too early to provide specifics on our clinical plans for these indications, we can reiterate that CDK 4/6 inhibitor refractory hormone receptor positive, HER2-negative metastatic breast cancer is an area of particular focus. We recently identified a principal investigator and breast cancer international key opinion leader to lead the trial. I look forward to providing further details as our clinical plans are finalized. We have recently developed very encouraging data in mantle cell lymphoma cell lines with the narazaciclib. This data will be submitted to a major medical meeting. Shifting gears, I'll now briefly discuss rigosertib certain, which as a reminder, as a multi faceted mechanism of action, targeting the RAS and polo-like kinase 1 pathways and the tumor immune microenvironment. We are utilizing investigator sponsored trials to advance rigosertib in several indications, and I'm making impressive progress and will continue to present the data at medical meetings, as we most recently did at the ESMO conference. In early 2023, we expect the initiation of an investigator sponsored Phase 2 trial evaluating rigosertib in combination with a checkpoint inhibitor, pembrolizumab in checkpoint inhibitor refractory malignant melanoma. In addition, the investigator sponsored trial a rigosertib monotherapy in squamous cell carcinoma of the skin associated with recessive dystrophic epidermolysis bullosa, commonly referred to as RDEB continues to enroll patients, and was recently the subject of a non-diluted grant to continue is very important clinical trial in these desperate patients. Initial single patient data in this ultra rare genetic disease indicates and continues to show a sustained, complete response with the patient now on therapy for over 15 months in complete response, and we have additional patients being enrolled. We believe this impressive response with proof contract for rigosertib [indiscernible] inhibit polo-like kinase one may have important implications, both in RDEB associated [indiscernible] and other more prevalent squamous cell indications given the central role of the polo-like kinase pathway in various cancers. With that, I'll now turn the call over to Dr. Gelder to speak more about narazaciclib's upcoming endometrial cancer trial and the reason ESMO presentation on rigosertib nivolumab combination therapy in KRAS mutated non-small cell lung cancer. Mark?