Thomas M. Brundage

CMX001 to Prevent Cytomegalovirus Disease in Hematopoietic-Cell Transplantation

BACKGROUND The use of available antiviral agents for the prevention of cytomegalovirus (CMV) disease is limited by frequent toxic effects and the emergence of resistance. CMX001 has potent in vitro activity against CMV and other double-stranded DNA viruses. We evaluated the safety and anti-CMV activity of CMX001 in patients who had undergone allogeneic hematopoietic-cell transplantation. METHODS From December 2009 through June 2011, a total of 230 patients with data that could be evaluated were enrolled in the study. We randomly assigned these adult CMV-seropositive transplant recipients from 27 centers to oral administration of CMX001 or placebo. Patients were assigned in a 3:1 ratio to five sequential study cohorts according to a dose-escalating, double-blind design. Randomization was stratified according to the presence or absence of acute graft-versus-host disease and CMV DNA in plasma. Patients received the study drug after engraftment for 9 to 11 weeks, until week 13 after transplantation. Polymerase-chain-reaction analysis of CMV DNA in plasma was performed weekly. Patients in whom CMV DNA was detected at a level that required treatment discontinued the study drug and received preemptive treatment against CMV infection. The primary end point was a CMV event, defined as CMV disease or a plasma CMV DNA level greater than 200 copies per milliliter when the study drug was discontinued. The analysis was conducted in the intention-to-treat population. RESULTS The incidence of CMV events was significantly lower among patients who received CMX001 at a dose of 100 mg twice weekly than among patients who received placebo (10% vs. 37%; risk difference, -27 percentage points; 95% confidence interval, -42 to -12; P=0.002). Diarrhea was the most common adverse event in patients receiving CMX001 at doses of 200 mg weekly or higher and was dose-limiting at 200 mg twice weekly. Myelosuppression and nephrotoxicity were not observed. CONCLUSIONS Treatment with oral CMX001 at a dose of 100 mg twice weekly significantly reduced the incidence of CMV events in recipients of hematopoietic-cell transplants. Diarrhea was dose-limiting in this population at a dose of 200 mg twice weekly. (Funded by Chimerix; CMX001-201 ClinicalTrials.gov number, NCT00942305.).

Brincidofovir for Asymptomatic Adenovirus Viremia in Pediatric and Adult Allogeneic Hematopoietic Cell Transplant Recipients: A Randomized Placebo-Controlled Phase II Trial

Adenovirus infection in immunocompromised patients contributes to significant morbidity and mortality, especially after allogeneic hematopoietic cell transplantation (HCT). Brincidofovir (BCV, CMX001) is an orally bioavailable lipid conjugate of cidofovir that has in vitro activity against adenoviruses and other double-stranded DNA viruses. This randomized placebo-controlled phase II trial evaluated pre-emptive treatment with BCV for the prevention of adenovirus disease in pediatric and adult allogeneic HCT recipients with asymptomatic adenovirus viremia. Allogeneic HCT recipients with adenovirus viremia were randomized 1:1:1 to receive oral BCV 100 mg (2 mg/kg if <50 kg) twice weekly (BIW), BCV 200 mg (4 mg/kg if <50 kg) once weekly (QW), or placebo for 6 to 12 weeks, followed by 4 weeks of post-treatment follow-up. For randomization, subjects were stratified by screening absolute lymphocyte count (<300 cells/mm3 versus ≥300 cells/mm3). Assignment to BCV or placebo was double blinded; dose frequency was unblinded. The primary endpoint was the proportion of subjects experiencing treatment failure, defined as either progression to probable or definitive adenovirus disease or confirmed increasing adenovirus viremia (≥1 log10 copies/mL) during randomized therapy. Between June 2011 and December 2012, 48 subjects were randomized to the BCV BIW (n = 14), BCV QW (n = 16), or placebo (n = 18) groups. The proportion of subjects with treatment failure in the BCV BIW group was 21% (odds ratio, .53; 95% confidence interval [CI], .11 to 2.71; P = .45), 38% (odds ratio, 1.23; 95% CI, .30 to 5.05, P = .779) in the BCV QW group, and 33% in the placebo group. All-cause mortality was lower in the BCV BIW (14%) and BCV QW groups (31%) relative to the placebo group (39%), but these differences were not statistically significant. After 1 week of therapy, 8 of 12 subjects (67%) randomized to BCV BIW had undetectable adenovirus viremia (<100 copies/mL), compared with 4 of 14 subjects (29%) randomized to BCV QW and 5 of 15 subjects (33%) randomized to placebo. In a post hoc analysis of subjects with viremia ≥1000 copies/mL at baseline, 6 of 7 BCV BIW subjects (86%) achieved undetectable viremia compared with 2 of 8 placebo subjects (25%; P = .04). Early treatment discontinuation because of adverse events was more common in subjects treated with BCV than with placebo. Diarrhea was the most common event in all groups (57% BCV BIW, 38% BCV QW, 28% placebo), but it led to treatment discontinuation in only 1 subject receiving BCV QW. Events diagnosed as acute graft-versus-host disease, primarily of the gastrointestinal tract, were more frequent in the BCV BIW group (50%) than in the BCV QW (25%) and placebo (17%) groups. There was no evidence of myelotoxicity or nephrotoxicity in BCV-treated subjects. The results of this trial confirm the antiviral activity of BCV against adenoviruses. Further investigation is ongoing to define the optimal treatment strategy for HCT recipients with serious adenovirus infection and disease.

Short-term clinical safety profile of brincidofovir: A favorable benefit-risk proposition in the treatment of smallpox.

Abstract Brincidofovir (BCV, CMX001) is an orally available, long‐acting, broad‐spectrum antiviral that has been evaluated in healthy subjects in Phase I studies and in hematopoietic cell transplant recipients and other immunocompromised patients in Phase II/III clinical trials for the prevention and treatment of cytomegalovirus and adenovirus infections. BCV has also shown in vitro activity against orthopoxviruses such as variola (smallpox) virus, and is under advanced development as a treatment for smallpox under the US FDAs ‘Animal Rule’. The anticipated treatment regimen for smallpox is a total weekly dose of 200 mg administered orally for 3 consecutive weeks. To assess the benefit‐to‐risk profile of BCV for the treatment of smallpox, we evaluated short‐term safety data associated with comparable doses from Phase I studies and from adult and pediatric subjects in the cytomegalovirus and adenovirus clinical programs. When administered at doses and durations similar to that proposed for the treatment of smallpox, BCV was generally well tolerated in both adults and pediatric subjects. The most common adverse events were mild gastrointestinal events and asymptomatic, transient, and reversible elevations in serum transaminases. The data presented herein indicate a favorable safety profile for BCV for the treatment of smallpox, and support its continued development for this indication. HighlightsBrincidofovir has potent antiviral activity in animal models of smallpox infection.A 3‐week treatment course is projected for the treatment of smallpox.Safety data from clinical studies in healthy adults receiving relevant brincidofovir doses or dose intervals are described.Three‐week safety data from clinical trials in adult and pediatric patients treated for viral infections are summarized.Short‐term dosing (3 weeks) necessary for the treatment of smallpox appears to be safe and well tolerated.

Brincidofovir Is Not A Substrate For The Human Organic Anion Transporter 1 (Oat1): A Mechanistic Explanation For The Lack Of Nephrotoxicity Observed In Clinical Studies.

Background: Brincidofovir (BCV) is an orally bioavailable lipid conjugate of cidofovir (CDV) with increased in vitro potency relative to CDV against all 5 families of double-stranded DNA viruses that cause human disease. After intravenous (IV) administration of CDV, the organic anion transporter 1 (OAT1) transports CDV from the blood into the renal proximal tubule epithelial cells with resulting dose-limiting nephrotoxicity. Objective: To study whether OAT1 transports BCV and to evaluate the pharmacokinetic and renal safety profile of oral BCV compared with IV CDV. Methods: The cellular uptake of BCV and its major metabolites was assessed in vitro. Renal function at baseline and during and after treatment in subjects in BCV clinical studies was examined. Results: In OAT1-expressing cells, uptake of BCV and its 2 major metabolites (CMX103 and CMX064) was the same as in mock-transfected control cells and was not inhibited by the OAT inhibitor probenecid. In human pharmacokinetic studies, BCV administration at therapeutic doses resulted in detection of CDV as a circulating metabolite; peak CDV plasma concentrations after oral BCV administration in humans were <1% of those observed after IV CDV administration at therapeutic doses. Analysis of renal function and adverse events from 3 BCV clinical studies in immunocompromised adult and pediatric subjects indicated little to no evidence of associated nephrotoxicity. Over 80% of subjects who switched from CDV or foscarnet to BCV experienced an improvement in renal function as measured by maximum on-treatment estimated glomerular filtration rate. Conclusions: The lack of BCV uptake through OAT1, together with lower CDV concentrations after oral BCV compared with IV CDV administration, likely explains the superior renal safety profile observed in immunocompromised subjects receiving BCV compared with CDV.

Efficacy of delayed brincidofovir treatment against a lethal rabbitpox virus challenge in New Zealand White rabbits

Abstract In the event of a bioterror attack with variola virus (smallpox), exposure may only be identified following onset of fever. To determine if antiviral therapy with brincidofovir (BCV; CMX001) initiated at, or following, onset of fever could prevent severe illness and death, a lethal rabbitpox model was used. BCV is in advanced development as an antiviral for the treatment of smallpox under the US Food and Drug Administrations ‘Animal Rule’. This pivotal study assessed the efficacy of immediate versus delayed treatment with BCV following onset of symptomatic disease in New Zealand White rabbits intradermally inoculated with a lethal rabbitpox virus (RPXV), strain Utrecht. Infected rabbits with confirmed fever were randomized to blinded treatment with placebo, BCV, or BCV delayed by 24, 48, or 72 h. The primary objective evaluated the survival benefit with BCV treatment. The assessment of reduction in the severity and progression of clinical events associated with RPXV were secondary objectives. Clinically and statistically significant reductions in mortality were observed when BCV was initiated up to 48 h following the onset of fever; survival rates were 100%, 93%, and 93% in the immediate treatment, 24‐h, and 48‐h delayed treatment groups, respectively, versus 48% in the placebo group (p < 0.05 for each vs. placebo). Significant improvements in clinical and virologic parameters were also observed. These findings provide a scientific rationale for therapeutic intervention with BCV in the event of a smallpox outbreak when vaccination is contraindicated or when diagnosis follows the appearance of clinical signs and symptoms. HighlightsBrincidofovir (BCV) reduced mortality from rabbitpox virus infection administered at or before the midpoint of disease.BCV treatment was associated with decreased peak viral loads, which may reduce disease infectivity.BCV does not prevent the development of post‐exposure immunity.BCV is a smallpox treatment option in populations where vaccination may be contraindicated.

A randomized, double-blind, placebo-controlled phase 3 trial of oral brincidofovir for cytomegalovirus prophylaxis in allogeneic hematopoietic-cell transplantation

Cytomegalovirus (CMV) infection is a common complication of allogeneic hematopoietic cell transplantation (HCT). In this trial, we randomized adult CMV-seropositive HCT recipients without CMV viremia at screening 2:1 to receive brincidofovir or placebo until week 14 post-HCT. Randomization was stratified by center and risk of CMV infection. Patients were assessed weekly through week 15 and every third week thereafter through week 24 post-HCT. Patients who developed clinically significant CMV infection (CS-CMVi; CMV viremia requiring preemptive therapy or CMV disease) discontinued the study drug and began anti-CMV treatment. The primary endpoint was the proportion of patients with CS-CMVi through week 24 post-HCT; patients who discontinued the trial or with missing data were imputed as primary endpoint events. Between August 2013 and June 2015, 452 patients were randomized at a median of 15 days after HCT and received study drug. The proportion of patients who developed CS-CMVi or were imputed as having a primary endpoint event through week 24 was similar between brincidofovir-treated patients and placebo recipients (155 of 303 [51.2%] versus 78 of 149 [52.3%]; odds ratio, .95 [95% confidence interval, .64 to 1.41]; P = .805); fewer brincidofovir recipients developed CMV viremia through week 14 compared with placebo recipients (41.6%; P < .001). Serious adverse events were more frequent among brincidofovir recipients (57.1% versus 37.6%), driven by acute graft-versus-host disease (32.3% versus 6.0%) and diarrhea (6.9% versus 2.7%). Week 24 all-cause mortality was 15.5% among brincidofovir recipients and 10.1% among placebo recipients. Brincidofovir did not reduce CS-CMVi by week 24 post-HCT and was associated with gastrointestinal toxicity.

Brincidofovir Decreases Adenovirus Viral Burden, Which is Associated with Improved Mortality in Pediatric Allogeneic Hematopoietic Cell Transplant Recipients

Background: Adenovirus (AdV) infection is an important cause of morbidity and mortality after hematopoietic cell transplant (HCT). Cidofovir is often used off-label to treat AdV viremia but does not lead to resolution of viremia without T cell immune reconstitution [1]. Brincidofovir (BCV) is an investigational antiviral with high potency in vitro against all AdV subtypes. BCV was evaluated as a treatment for AdV infection or disease in pediatric allogeneic HCT recipients in the AdVise trial (CMX001-304; NCT02087306); primary analyses were previously presented [2]. Herein we further analyze the effect of BCV on AdV viral burden in the subgroup of pediatric HCT patients with clinically significant AdV viremia (≥1000 copies/mL) within 100 days of transplant, and examine the correlation of viral burden with clinical outcome. Methods: In the AdVise trial, patients were treated with oral BCV 2 mg/kg (up to 100 mg) twice weekly for 12 weeks and followed for 36 weeks post-first dose. AdV viremia outcomes were assessed at multiple time points, including clearance of viremia, reductions in viremia, time to clearance, time undetectable, time under 1000 copies/mL, and viral burden measured as area under the viremia-time curve (AUC) and time-averaged area under the viremia-time curve (AAUC). Associations between these viral responses and mortality were examined. Results: Of the 100 pediatric allo HCT patients enrolled in the AdVise trial, 40 presented with AdV viremia ≥1000 copies/ mL within 100 days of transplant. Thirty-four (85%) cleared the virus on BCV, with a median (IQR) time to clearance of 22 (15, 38) days. Twenty-one (53%) of these 40 patients were alive at Week 36. Mean (SD) Week 12 AAUC was 2.4 (.5) log10 c/mL in patients alive at Week 36 versus 3.3 (1.7) log10 c/mL in patients who died prior to Week 36 (see Figure 1; Satterthwaite t-test P = .038). Baseline AdV viremia was positively correlated with AAUC (R2 = .30). Conclusions: Rapid declines in AdV viral load, clearance of AdV, and reductions in AdV viral burden were observed in pediatric allogeneic HCT recipients treated with BCV. Viral responses were associated with improved survival. These data support continued development of BCV as the first potential therapeutic for AdV.