Safety and Efficacy of CBX129801 in Patients With Type 1 Diabetes

Key Inclusion Criteria: * Give informed consent; * 18-65 years old; * Have type 1 diabetes mellitus for a minimum of 5 years, with a stable diabetic regimen (for at least 3 months); * Have clinical signs of diabetic peripheral neuropathy at screening; * Have abnormal sural nerve conduction observed bilaterally during screening; * Be C-peptide deficient; * Be in good general health (besides having type 1 diabetes mellitus); * Practice effective contraception during and for at least 12 weeks after study participation; * Have a body mass index (BMI) ≥18.0 and \<35.0 kg/m2. Key Exclusion Criteria: * Any significant cardiovascular, hematological, lymphatic, immunologic, urologic, dermatologic, psychiatric, renal, hepatic, pulmonary, endocrine (except for diabetes mellitus), central nervous, gastrointestinal, or other major disease; * Unstable or inadequate glucose control; * Any clinically significant laboratory value at screening; * Occurrence of a severe, unexplainable hypoglycemic event (defined as requiring the assistance of another individual) within 6 months of Day 0, or recurrent episodes of non-severe hypoglycemia (≥3 per week on average) that are deemed clinically significant by the Investigator; * Have had an islet cell, kidney, and/or pancreas transplant; * If female, is pregnant or lactating; * History of alcohol or substance abuse within 2 years; * Positive screen for hepatitis B, hepatitis C antibody, or human immunodeficiency virus (HIV) antibody; * Initiation of treatment or change of dose of medication that could affect peripheral nerve function within 60 days; * Previous treatment with CBX129801 or unmodified C-peptide; * Receipt of an investigational product or therapeutic device, or participation in a drug research study, within a period of 30 days; * Chronic use of oral steroids or use of Ampyra (dalfampridine) within 60 days.