Part 1: This is a randomised, double-blind, placebo-controlled, multiple ascending dose design to assess the safety, tolerability and PK profile of multiple doses of LYT-100 administered under fed conditions at steady state in healthy participants. Up to 4 dosing cohorts are planned.

Part 2: The dose level immediately below the maximally tolerated dose in Part 1 will be used in Part 2. Following a minimum 7-day washout of the cohort that received this dose, subjects in Part 2 will be administered a single dose of their assigned treatment under fasting conditions to permit a comparison of the rate and extent of absorption of LYT-100 under fasting conditions to the equivalent dose in a prior fed cohort.

Part 3: Once the optimal dose and regimen is determined with or without food, Part 3 will follow with an open-label, single treatment arm to assess the safety, tolerability, PK, biomarkers and effect on exploratory clinical endpoints of LYT-100 over a period of up to 6-months of dosing in breast carcinoma patients with secondary lymphoedema following sentinel lymph node biopsy and/or axillary node dissection, with or without radiation.