The main purpose of this study is to determine the safety and efficacy of LY3556050 versus placebo in participants with diabetic peripheral neuropathic pain (DPNP). The study will lasts approximately 24 weeks, across 3 study periods.

Inclusion Criteria:

• Have a history and current diagnosis of Type 1 Diabetes (T1D) or Type 2 Diabetes (T2D) diagnosed for at least 6 months prior to screening.

• Have a stable glycemic control on stable diabetes treatment regimen for at least 90 days prior to day 1 with a hemoglobin A1c (HbA1c) ≤10 for T1D and HbA1c ≤11 for participants with T2D at time of screening.

• Have a history of daily peripheral neuropathic pain for at least 12 weeks based on participant report or medical history.

• Have a visual analog scale (VAS) pain value ≥40 and <95 during screening.

• Have presence of diabetic peripheral neuropathy of symmetrical nature and in lower extremities for ≥6 months and diagnosed by a score of Part B ≥3 on Michigan Neuropathy Screening Instrument

• Are willing to maintain a consistent regimen of any ongoing nonpharmacologic pain-relieving therapies (for example, physical therapy) and will not start any new nonpharmacologic pain-relieving therapies during study participation.

• Are willing to discontinue all medications taken for chronic pain conditions, except allowed concomitant pain medication permitted per protocol, for the duration of the study

  • Have a body mass index ≤45 kilogram/square meter (kg/m²) (inclusive).
  • Are men, or women able to abide by reproductive and contraceptive requirements.

Exclusion Criteria:

• History of other potentially causative and/or confounding sources of pain that may impair self-assessment of pain due to DPNP.
• Have had a procedure within the past 6 months intended to produce permanent sensory loss in the target area of interest (for example, ablation techniques.
• Have had cancer within 2 years of baseline, except for cutaneous basal cell or squamous cell carcinoma resolved by excision.
• Are, in the judgment of the investigator, actively suicidal and therefore deemed to be at significant risk for suicide.
• Have in the judgement of the investigator, an acute, serious, or unstable medical condition or a history or presence of any other medical illness that would preclude study participation.
• Have a positive HIV test result at screening.
• Have a surgery planned during the study for any reason.
• Have a substance use disorder as defined by the Diagnostic and Statistical Manual of Mental Disorders (5th edition; DSM-5; American Psychiatric Association)

Anonymized individual patient level data will be provided in a secure access environment upon approval of a research proposal and a signed data sharing agreement.

Data are available 6 months after the primary publication and approval of the indication studied in the US and European Union (EU), whichever is later. Data will be indefinitely available for requesting.

A research proposal must be approved by an independent review panel and researchers must sign a data sharing agreement.