Mass General - Division of Clinical Research

(To be used in conjunction with Platform Protocol criteria.) 1. At the time of screening (V1), a documented diagnosis of stable Type II diabetes mellitus with painful diabetic peripheral neuropathy of at least 6 months' duration with BOTH of the following as confirmed by a physician trained for the study: 1. Neuropathic symptoms in a distal distribution (e.g., numbness, paresthesia or tingling, sensory distortions or misinterpretations, etc.) 2. Decreased distal sensation (e.g., decreased vibration, pinprick sensation, light touch, etc.) 2. A score ≥3 on the Michigan Neuropathy Screening Instrument (MNSI) part B. Diagnosis must be carried out by trained personnel. 3. At the time of screening (V1) at least 40 mm on a 100-mm visual analog scale (VAS) for average pain over the previous 24 hours. 4. Patient-reported daily 11-point NRS (for average pain over the last 24 hours) meets the criteria specified in "Appendix B: Blinded Information" during both the 7-day screening and 7-day baseline periods. The algorithm will be assessed centrally.

(To be used in conjunction with Platform Protocol criteria.) Participants fulfilling any of the following criteria are not eligible for the study. 1. Females of childbearing potential will be excluded. Any of the following criteria will suffice to confirm a female's inability to bear children: 1. Previous bilateral salpingectomy, bilateral salpingo-oophorectomy, or hysterectomy; 2. Postmenopausal state (defined as 12 consecutive months of spontaneous amenorrhea without an alternative medical reason in a woman of at least 50 years of age); 3. Premature ovarian failure (confirmed by a specialist), XY genotype, Turner syndrome, uterine agenesis. 2. Body mass index of > 40 kg/m2. 3. Diagnosis of alcohol or substance abuse or dependence (other than nicotine or caffeine) within the 2 years before the Screening visit. 4. Moderate or severe renal impairment, known (documented) or defined as an estimated/calculated creatinine clearance/estimated glomerular filtration rate (eGFR) < 45 mL/min/1.73 m2, according to the Chronic Kidney Disease Epidemiology Collaboration formula. 5. Any of the following conditions related to corrected QT intervals using Fridericia's formula (QTcF): 1. A QTcF > 500 ms prior to starting IP. 2. A history of the following additional risk factors for torsade de pointes: heart failure, hypokalemia, history or family history of long QT syndrome. 6. History of myocardial infarction, arrhythmia, other significant heart disease, or stroke. 7. History of gastric surgery that might be expected to alter normal absorption of the IP (e.g., gastric bypass). 8. Participants known to have participated in four or more studies for investigational pain drugs. 9. Participants known to be non-responders to more than three previous neuropathic pain medications at adequate doses over at least 4 weeks or to have discontinued more than three such medications due to tolerability. Adequate doses (given as total daily doses) are defined as follows: 1,800 mg gabapentin; 300 mg pregabalin; opioid analgesics 60 mg oxycodone equivalent or 200 mg tramadol; 75 mg amitriptyline or equivalent tricyclic antidepressant; 60 mg duloxetine; 150 mg venlafaxine. 10. Known hypersensitivity or contraindication to any excipients of the study drug formulation. 11. Taking prohibited medications as described in Section 12, "Concomitant Therapy," and Appendix A, "Prohibited Medications." 12. Major depressive episode within the 6 months before screening and/or a history of diagnosed recurrent major depressive disorder. 13. Any of the following conditions related to suicidality: 1. Any suicidal ideation with intent, with or without a plan, at screening, i.e., answering "yes" to questions 4 or 5 on the Suicidal Ideation section of the Baseline/Screening version of the Columbia-Suicide Severity Rating Scale (C-SSRS); 2. Answering "yes" on any item of the Suicidal Behavior Section (except for the "non-suicidal self-injurious behavior") of the C-SSRS if this behavior occurred in the past 2 years; 3. A lifetime history of suicide attempt (V1). 14. Previous known or possible exposure to NRD135S.E1.