Preliminary Results from the AdVise Study Evaluating Brincidofovir (CMX001, BCV) for the Treatment of Disseminated and High-Risk Adenovirus (AdV) Infection

Discovery of a Small Molecule Inhibitor of Human Adenovirus Capable of Preventing Escape from the Endosome

Human adenoviruses (HAdVs) display a wide range of tissue tropism and can cause an array of symptoms from mild respiratory illnesses to disseminated and life-threatening infections in immunocompromised individuals. However, no antiviral drug has been approved specifically for the treatment of HAdV infections. Herein, we report our continued efforts to optimize salicylamide derivatives and discover compound 16 (JMX0493) as a potent inhibitor of HAdV infection. Compound 16 displays submicromolar IC₅₀ values, a higher selectivity index (SI > 100) and 2.5-fold virus yield reduction compared to our hit compound niclosamide. Moreover, unlike niclosamide, our mechanistic studies suggest that the antiviral activity of compound 16 against HAdV is achieved through the inhibition of viral particle escape from the endosome, which bars subsequent uncoating and the presentation of lytic protein VI.

Discovery of Novel Substituted N-(4-Amino-2-chlorophenyl)-5-chloro-2-hydroxybenzamide Analogues as Potent Human Adenovirus Inhibitors

An effective therapy for human adenovirus (HAdV) infections in immunocompromised patients and healthy individuals with community-acquired pneumonia remains an unmet medical need. We herein reported a series of novel substituted N-(4-amino-2-chlorophenyl)-5-chloro-2-hydroxybenzamide analogues as potent HAdV inhibitors. Compounds 6, 15, 29, 40, 43, 46, 47, and 54 exhibited increased selectivity indexes (SI > 100) compared to the lead compound niclosamide, while maintaining sub-micromolar to low micromolar potency against HAdV. The preliminary mechanistic studies indicated that compounds 6 and 43 possibly target the HAdV DNA replication process, while compounds 46 and 47 suppress later steps of HAdV life cycle. Notably, among these derivatives, compound 15 showed improved anti-HAdV activity (IC₅₀ = 0.27 μM), significantly decreased cytotoxicity (CC₅₀ = 156.8 μM), and low in vivo toxicity (maximum tolerated dose = 150 mg/kg in hamster) as compared with niclosamide, supporting its further in vivo efficacy studies for the treatment of HAdV infections.

Structure-Activity Relationship Studies on Diversified Salicylamide Derivatives as Potent Inhibitors of Human Adenovirus Infection

The effective treatment of adenovirus (HAdV) infections in immunocompromised patients still poses great challenges. Herein, we reported our continued efforts to optimize a series of salicylamide derivatives as potent inhibitors of HAdV infection. Of these, nine compounds (11, 13, 14, 17, 20, 58, 60, 62, and 70) showed significantly improved anti-HAdV activities with nanomolar to submicromolar IC₅₀ values and high selectivity indexes (SI > 100), indicating better safety windows, compared to those of the lead compound niclosamide. Our mechanistic assays suggest that compounds 13, 62, and 70 exert their activities in the HAdV entry pathway, while compounds 14 and 60 likely target the HAdV DNA replication, and 11, 17, 20, and 58 inhibit later steps after DNA replication. Given the broad anti-viral activity profile of niclosamide, these derivatives may also offer therapeutic potential for other viral infections.

Drug development against human adenoviruses and its advancement by Syrian hamster models

The symptoms of human adenovirus infections are generally mild and self-limiting. However, these infections have been gaining importance in recent years because of a growing number of immunocompromised patients. Solid organ and hematopoietic stem cell transplant patients are subjected to severe immunosuppressive regimes and cannot efficaciously eliminate virus infections. In these patients, adenovirus infections can develop into deadly multi-organ disseminated disease. Presently, in the absence of approved therapies, physicians rely on drugs developed for other purposes to treat adenovirus infections. As there is a need for anti-adenoviral therapies, researchers have been developing new agents and repurposing existing ones to treat adenovirus infections. There are several small molecule drugs that are being tested for their efficacy against human adenoviruses; some of these have reached clinical trials, while others are still in the preclinical phase. Besides these compounds, research on immunotherapy against adenoviral infection has made significant progress, promising another modality for treatment. The availability of an animal model confirmed the activity of some drugs already in clinical use while proving that others are inactive. This led to the identification of several lead compounds that await further development. In the present article, we review the current status of anti-adenoviral therapies and their advancement by in vivo studies in the Syrian hamster model.

Adenovirus Viremia in Adult CD34(+) Selected Hematopoietic Cell Transplant Recipients: Low Incidence and High Clinical Impact

Adenovirus (ADV) infections after hematopoietic cell transplantation (HCT) range in severity from self-limited to fatal. We have previously reported high mortality rates in CD34(+) selected T cell-depleted (TCD) HCT recipients using symptomatic testing and culture methods for ADV detection. We report rates and outcomes of ADV viremia in 215 adult recipients of TCD HCT using the CliniMACS CD34(+) selection system. This was a prospective observational study of adults transplanted from March 21, 2012 through November 30, 2014 at Memorial Sloan-Kettering Cancer Center. TCD was performed using CliniMACS CD34(+) cell selection. Patients were monitored for ADV by whole blood PCR assay from +14 to +100 days post-transplant. ADV viremia was defined as ≥1 PCR above the lower limit of quantitation. ADV disease was defined per European Group for Blood and Marrow Transplantation guidelines. Treatment for ADV was at the clinician's discretion. Competing risk regression analyses were used to identify predictors for ADV viremia and overall survival. The median age was 55 years (range, 22 to 72); 215 patients underwent TCD. All patients received myeloablative conditioning. Eighteen patients (8% of cohort) had ADV viremia at a median onset of 57 days (interquartile range [IQR], 23 to 79) and with a median viral load at first detection of 2.6 log10 copies/mL (IQR, 2.5 to 4.0). The median maximal viral load was 4.5 log10 copies/mL (IQR, 3.5 to 5.9). No significant risk factor was identified for ADV viremia by univariate analysis. Six patients (3% of total cohort, 33% of viremic patients) developed ADV disease (3 colitis, 2 nephritis/cystitis, 1 pneumonitis). ADV viremia preceded onset of ADV disease a median of 11 days from the first positive quantitative PCR (range, +3 to +37) except in 1 patient with nephritis. Overall, 12 of 18 viremic patients (67%) received antiviral treatment (5 cidofovir only, 7 brincidofovir ± cidofovir). All patients with ADV disease were treated, and 6 patients were preemptively treated for ADV. Among the 18 viremic patients, 8 (44%) died during the study period, and, of those, 4 (22%) died of ADV. Early ADV viremia was infrequent (8%) among adult HCT recipients of CD34(+) selected allografts. Among viremic patients, rate of ADV disease was 33% and ADV attributable mortality was 22%. Further studies are needed to assess the impact of preemptive treatment with brincidofovir on improving outcomes of ADV infections in this patient population.