The main purpose of this study is measure the effect of VI-0521 on kidney function. Specifically, glomerular filtration rate (GFR) will be measured at baseline, after 4 weeks of study treatment, and after an additional 4 weeks of off-treatment recovery.

This is a randomized, double-blind, placebo-controlled, single-site study in healthy overweight or obese male and female volunteers. Oral VI-0521 (combination of phentermine and topiramate [PHEN/TPM] extended-release capsule) will be administered daily as follows:

• Days 1-3: PHEN/TPM 3.75 mg /23 mg
• Days 4-6: PHEN/TPM 7.5 mg /46 mg
• Days 7-9: PHEN/TPM 11.25 mg /69 mg
• Days 10-28: PHEN/TPM 15 mg /92 mg

A single dose of Iohexol (a non-radioactive iodine-containing contrast agent) will be administered intravenously on three separate occasions.

The study will include a total of 50 healthy subjects (40 active and 10 placebo), all of whom will have overnight stays on 3 separate occasions.

Total study duration is approximately 10 weeks (2 weeks screening, 4 weeks study treatment, 4 weeks post treatment follow up).

Key Inclusion Criteria:

• Male or female 18 - 65 years of age, medically healthy with no clinically significant screening abnormalities
• BMI of ≥27 to ≤45 kg/m2
• No use of any medication (prescription, over the counter (OTC) or herbal preparations) with the exception of contraception for the entirety of the study

Key Exclusion Criteria:

• Allergy or hypersensitivity to radio contrast media, iodine or shellfish
• Plans to significantly alter their diet through fasting, very low caloric intake, elimination of certain foods (gluten, milk, meat, etc.) or similar
• Plans to undertake a significant change to physical exercise levels (i.e., initiate training for a marathon) during the study period
• Consumption of a high protein diet or protein/body building meal supplementation and/or replacement. The use of any product containing creatine is strictly prohibited
• History of glaucoma or increased intraocular pressure
• History of bipolar disorder or psychosis, history of psychiatric hospitalization, greater than one lifetime episode of major depression, current depression of moderate or greater severity, presence or history of suicidal behavior or ideation with some intent to act on it
• Cholelithiasis (gallstones) within the past 6 months
• History of nephrolithiasis (kidney stones)
• Evidence of any clinically significant renal, pulmonary, hepatic, psychiatric or other condition by history, physical examination or laboratory studies that, in the opinion of the investigator, would contraindicate the administration of study medications, affect compliance, interfere with study evaluations or confound the interpretation of study results as determined by the investigator
• Current use of any tobacco products including cigarettes, cigars, pipes, and chewing tobacco, or nicotine replacement products (e.g., patch, gum, lozenge, etc.), or chronic use within the previous three months prior to screening

3 months