This is a multicenter, randomized, double-blind, parallel-group, 2 treatment group, repeated dose study to compare the PK, efficacy, safety, and immunogenicity of AVT32-DRL\_PB (proposed Keytruda® biosimilar) versus Keytruda (pembrolizumab) when administered as monotherapy in participants with fully resected Stage IIB/C or Stage III melanoma requiring adjuvant treatment with pembrolizumab. Eligible participants will be randomized in a 1:1 ratio to the AVT32-DRL\_PB or Keytruda treatment group and stratified by sex (female versus male) and body weight category (≤75 kg versus \>75 kg). Study treatments will be administered every 3 weeks (Q3W) as an intravenous (IV) infusion over 30 minutes (1 administration Q3W is 1 treatment cycle). The administered pembrolizumab dose will be 200 mg Q3W for both treatment groups.