Lack of Effect of CMX001 on Renal and Myeloid Parameters in Humans, Monkeys, and Rodents W Painter, RS Verhoeven, AT Robertson, H Mommeja-Marin, GR Painter, and LC Trost Chimerix, Inc., Durham, North Carolina USA Congress of the European Societies for Toxicology 17-20 June 2012 Abstract # 203/269 INTRODUCTION RESULTS RESULTS CMX001 is a novel, phospholipid-modified small molecule (NCE) (acyclic nucleotide) providing unique intracellular delivery of a potent antiviral, broadly active against multiple dsDNA viruses through inhibition of DNA polymerase. CMX001 is in development for prevention and treatment of CMV and adenovirus in transplant recipients and as a therapeutic countermeasure for smallpox. CMX001, was designed to take advantage of the broad-spectrum antiviral activity of cidofovir while eliminating its dose-limiting renal toxicity. CMX001 is stable in plasma and generates high intracellular concentrations of the active antiviral while concentrations of circulating CDV remain low. Studies in animals and humans have been conducted to evaluate the safety of CMX001. Toxicology Studies Clinical Studies Table 3. Toxicology Studies in Rats and Monkeys: Clinical Pathology Parameters of Nephro- and Myelotoxicity, Percent Change From Control Table 5. Clinical Studies in Humans: Clinical Pathology Parameters of Nephro- and Myelotoxicity Parameter Week 13 in Rats 15 mg/kg Week 13 in Monkeys Week 39 in Monkeys 25 mg/kg Urinalysis No CMX001-related effects No CMX001- related effects Creatinine* -1.6% -6.3% +9.5% BUN* -2.4% -4.2% +5.3% WBC* +16.8% +2.8% +15.8% ANC* +7.7% +29.7% +29.2% Platelets* +2.1% -0.2% -6.1% Parameter Duration of CMX001 dosing Adults Pediatrics N= Median change from Baseline Median change from Baseline Creatinine (mg/dL) < 4 weeks 92 59 -0.01   Week 4 61 45 0.00 Week 8 20 -0.07 31 -0.10 Week 12 11 -0.40 19 -0.04 BUN (mg/dL) 86 2 57 3 4 44 -3 30 5 1 WBC (x10^3/uL) 34 0.04 26 0.36 12 16 0.22 6 0.17 8 0.21 ANC (x10^3/µL) 79 0.20 53 52 0.60 40 -0.02 15 -0.50 25 0.52 -0.15 Platelets (x10^3/µL) 58 60 -2 10 -5 7 -11 18 CMX001 * Percent change in mean high dose value compared to control METHODS No CMX001-related findings were noted in the assessment of clinical pathology parameters indicative of nephrotoxicity or myelosuppression following twice weekly oral administration for 13 weeks in rats or 39 weeks in monkeys. Toxicology Studies GLP toxicology and toxicokinetic studies of CMX001 administered twice weekly by the oral route were conducted in Sprague-Dawley rats at durations up to 13 weeks and in cynomolgus monkeys at durations up to 39 weeks at doses >10 fold the anticipated clinical dose. Standard toxicology endpoints were evaluated in all animal studies, including body weight, food consumption, clinical observations, clinical pathology, organ weights, gross observations at necropsy, and histopathology of standard tissues. Changes in anatomic and clinical pathology parameters relevant to potential renal and hematologic effects are discussed. Table 4. Toxicology Studies in Rats and Monkeys: Histopathology Parameters of Nephro- and Myelotoxicity Parameter 13-Wk Study in Rats 13-Wk Study in Monkeys 39-Wk Study in Monkeys Bone Marrow Cellularity No CMX001- related effects No CMX001-related effects Kidney Weights Gross Observation of Kidneys Mild pale discoloration in 4 of 20 animals at 25 mg/kg Kidney Histopathology Minimal or mild karyomegaly of tubular epithelial cells in 13 of 20 animals at 25/mg/kg In this severely ill patient population there was no effect on hematologic parameters or on renal function as indicated by changes in BUN and creatinine. Table 6. Clinical Studies in Humans: Creatinine Concentrations Pre- and Post-treatment with CMX001 Table 1. Toxicology Studies of CMX001 Conducted in Rats and Monkeys Parameter Adults n = 87 Pediatrics n = 56 Baseline Post-Treatment Post- Treatment Mean (mg/dL) 1.59 1.67 0.83 0.82 SD 1.18 1.64 0.84 0.85 Median (mg/dL) 1.12 1.00 0.5  Species Rat Monkey Study Duration 13 Weeks 39 Weeks Animal Number 10/sex/group 4-6/sex/group Dose (mg/kg) Twice Weekly 0, 1, 4, 15 0, 5, 15, 25 Parameters Evaluated Hematology, serum chemistry, urinalysis, gross & microscopic pathology There were no changes in bone marrow cellularity indicative of myelotoxicity in either rats given up to 15 mg/kg CMX001 for 13 weeks or in monkeys given up to 25 mg/kg CMX001 for 39 weeks. Analysis of kidney weights, gross observations of the kidneys, and renal histopathology demonstrated that there were no test article-related effects in these tissues in either rats or monkeys following 13 weeks of administration. In the 39 week monkey study, diagnosable kidney change (minimal or mild karyomegaly) was observed in about half of the animals at the high dose (25 mg/kg). There were no related clinical pathology changes and the dose was well tolerated for the entire duration of the study. The changes were not dose-limiting and were judged to be related to exposure to CDV, a metabolite of CMX001 to which monkeys receive much higher relative exposure than humans following administration of CMX001 (AUCm/AUCp = 20 in monkeys vs 0.6 in humans, a 33-fold difference.) Many patients entered the study with pre-existing renal impairment (often due to previous treatment with CDV). There was no evidence of decreased renal function following treatment with CMX001 for up to 9 months as indicated by creatinine values prior to treatment compared with the value obtained following the last dose of CMX001. Clinical Studies Renal and hematologic parameters from 210 patients administered CMX001 either once or twice weekly under Emergency Investigational New Drug (EIND) regulations (or foreign equivalent). Subjects were treated in the US, Canada, France, Switzerland, Spain, United Kingdom, Austria, Israel and Chile. In the US, Emergency INDs were granted by the FDA for patients with life-threatening dsDNA viral infection with no treatment alternative, predominantly caused by CMV and adenovirus. SUMMARY Single doses of VISTIDE have been reported to cause acute renal failure and death. VISTIDE also has a black box warning for neutropenia. There were no changes in clinical or anatomic pathology parameters indicative of nephrotoxicity or myelosuppression following administration of CMX001 for up to 39 weeks in animals at doses exceeding the likely clinical dose by >10-fold Similarly, no changes in corresponding parameters were observed following up to 9 months of administration of CMX001 in patients, including those with pre-existing renal impairment. Table 2. Clinical Studies in Humans: Baseline Characteristics Characteristic Adults n=123 Pediatrics n=87 Gender Number(%) Male/Female   71 (58%)/52 (42%) 44 (51%)/42 (48%) Age (years) Median/Mean 50.4/48.9 7.6/8.0 Weight (kg) 70.1/71.2 26.0/30.0 Race (n (%)) Caucasian Black Asian Other Unknown* 59 (48%) 10 (8%) 7 (6%) 5 (4%) 42 (34%) 28 (32%) 12(14%) 1 (1%) 3 (4%) 43 (49%) CONCLUSION Unlike CDV and other antivirals used to treat severe dsDNA virus infections, there was no evidence of nephrotoxicity or myelosuppression associated with administration of CMX001 in animals at significant multiples of the anticipated clinical dose, or in humans administered CMX001 for treatment of life-threatening dsDNA viral infections. * Race was frequently not recorded REFERENCES ACKNOWLEDGEMENTS The authors would like to thank the staff of BASi, MPI, and SNBL for their work conducting the toxicology studies, as well as the clinicians and their patients. Lacy, et al. (1998). Effect of Oral Probenecid Coadministration on the Chronic Toxicity and Pharmacokinetics of Intravenous Cidofovir in Cynomolgus Monkeys. Tox. Sci. 44, 97-106 VISTIDE Summary Basis of Approval