Optimization of novel inhibitors of human cytomegalovirus

Summary: Human cytomegalovirus (CMV) is a β-herpes virus with high seroprevalence rates of 60-90% within the population that can spread through bodily fluids, organ transplants, and from mother to fetus via the placenta. Virus proliferation significantly increases the morbidity and mortality of immunocompromised individuals, such

as newborns, organ transplant recipients, AIDS patients, and the elderly. Approximately 30,000 solid organ transplant and 23,000 bone marrow transplants operations are performed in the U.S. every year. CMV is the leading cause of birth defects, affecting ~1% of newborns giving rise to ~30,000 new cases of CMV infection

reported annually in the US. While several drugs have been approved by the FDA for the treatment of CMV infections, including ganciclovir, foscarnet, letermovir, and recently maribavir, these compounds were found to exhibit high frequencies of drug resistance and severe side effects, including bone marrow toxicity,

gastrointestinal disruption, and nephrotoxicity. Given the large number of patient populations at risk for CMV- associated diseases and the estimated cost to treat CMV in the US ($4.4 billion/year by the National Academy of Sciences), novel therapeutic strategies to treat CMV-associated diseases is needed. The development of

novel therapeutics that target different steps of the viral life cycle to limit virus propagation and dissemination would provide therapeutic for treating CMV-related diseases. We developed a high-content screening assay using a CMV AD169 reporter virus to screen >112,000 compounds in collaboration with Microbiotix to identify

inhibitors that block the early stage of infection. One compound, MBXC-4302, is a N-arylpyrimidinamine (NAPA) that exhibited potent anti-CMV infection activity (IC50 ~3 µM), limited cytotoxicity (CC50 >100µM), favorable in vitro ADME properties, and a responsive structure activity relationship (SAR). Commercial analogs

of MBXC-4302 identified MBXC-4992 with an improved selective index. Our general hypothesis is that the NAPA compounds represent novel CMV entry inhibitors that can be developed into effective CMV therapeutics. To evaluate our hypothesis, we plan to complete the following Aims: 1) Characterize the mechanism of action and broad inhibition of the NAPA compounds; 2) Optimize the NAPA series through SAR-

driven analog generation; 3) Evaluate the ability of NAPA compounds to limit virus proliferation and dissemination in diverse in vitro models; and 4) Evaluate pharmacokinetics, tolerability, and efficacy of prioritized NAPA analogs in dissemination studies in vivo. We plan to develop several NAPA analogs as

effective CMV therapeutics that inhibit CMV dissemination as a single agent or in combination with FDA approved CMV drugs.