Study to Assess Analgesic Efficacy and Safety of ASP3662 in Subjects With Painful Diabetic Peripheral Neuropathy

Inclusion Criteria:

- Subject has a BMI ≤ 40.

- Subject has all of the following:

1. Established diagnosis of diabetes (Type I or II) with painful diabetic peripheral
neuropathy and glycosylated hemoglobin (HgbA1c) ≤ 9.5% at Screening or
Randomization.

2. Stable diabetic drug regimen for at least 3 months prior to Screening.

3. At least a 1 year history of PDPN.

4. Diagnosis of PDPN to be confirmed by a score of ≥ 3 on the Michigan Neuropathy
Screening Instrument (MNSI) at Screening.

- Subject has pain intensity score(s) ≥ 4 or ≤ 9 on an 11-point numeric pain rating
scale (NPRS) at Screening Visit and prior to Randomization.

- Subject agrees to complete pain diaries and is complaint with the daily pain recording
prior to Randomization as defined by the completion of a minimum of 5 of 7 daily pain
ratings, 3 of which are required in the last 4 days.

- Subject's anti-diabetic regimen is anticipated to be stable throughout the study.

- Subject must be willing to washout of all medications currently being taken for
his/her PDPN (chronic and occasional/as needed) and remain off of those pain
medications while participating in the study.

Exclusion Criteria:

- Subject has received prior treatment with pregabalin for PDPN and was considered
unresponsive or intolerant.

- Subject has tried and failed 3 or more drugs to treat PDPN within the past 3 years.
Drugs must have been administered at therapeutic doses and have been administered for
an adequate period of time.

- Subject has a known hypersensitivity to ASP3662, pregabalin, gabapentin or
acetaminophen, or their formulation components.

- Subject has significant pain (moderate or above) due to causes other than PDPN.

- Subject has a history of painful peripheral neuropathy due to a cause other than
diabetes.

- Subject has any lower extremity amputation

- Subject has a current or previous foot ulcer within the past 3 months as described by
medical history and/or medical examination.

- Subject has an active malignancy or a history of malignancy (except for treated
non-melanoma skin cancer) within 5 years.

- Subject has clinically significant abnormalities in clinical chemistry, hematology, or
urinalysis, or a serum creatinine at Screening.

- Subject has creatinine clearance < 60 mL/min (estimated from serum creatinine, body
weight, age, and sex using the Cockcroft and Gault equation) at Screening.

- Subject tests positive for hepatitis B surface antigen (HBsAg) or hepatitis C antibody
at Screening or has a known history of a positive test for human immunodeficiency
virus (HIV) infection.

- Subject has a positive drug screen for alcohol or drugs of abuse at Screening and/or
Randomization. Subjects who are on low doses of benzodiazepines for sleep with a
legitimate prescription will be allowed into the study. In addition, subjects with a
positive drug screen at Randomization will be excluded.

- Subject is currently using protocol specified non-permitted medications including OTC
products and is unable or does not choose to discontinue them.

- Subject has planned an elective surgery during planned study participation.