A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of RO7446603 Administered Alone or in Combination With Aflibercept or Faricimab in Participants With Diabetic Macular Edema

Inclusion Criteria: * Documented diagnosis of diabetes mellitus (DM) (Type 1 or Type 2) with glycated hemoglobin (HbA1c) \< 12% * Macular thickening secondary to DME involving the center of the fovea \> 325 microns * Decreased VA attributable primarily to DME between 25 and 73 ETDRS letters Exclusion Criteria: * Currently untreated DM or previously untreated participants who initiated oral anti-diabetic medication or insulin within 90 days prior to Day 1 * Uncontrolled blood pressure (BP) * Pregnancy or breastfeeding, or intention to become pregnant during the study * For Parts 1-4: IVT anti-VEGF treatment within 90 days prior to Day 1; For Part 5: IVT anti-VEGF treatment within 120 days prior to Day 1 or IVT anti-VEGF treatment prior to Day 1 for treatment naïve participants * Treatment with SUSVIMOTM (ranibizumab injection) prior to Day 1 * Any IVT or periocular (sub-tenons) corticosteroid treatment within 6 months prior to Day 1 * Any current or history of ocular disease other than DME that may confound assessment of the macula or affect central vision * Proliferative diabetic retinopathy (PDR) in the study eye * Active or history of uveitis, vitritis (grade trace or above), and/or scleritis in either eye Other protocol-specified inclusion/exclusion criteria may apply