Given a set of therapeutic epitopes, a cassette sequence is designed to reduce the likelihood that junction epitopes are presented in the patient. The cassette sequence is designed by taking into account presentation of junction epitopes that span the junction between a pair of therapeutic epitopes in the cassette. The cassette sequence may be designed based on a set of distance metrics each associated with a junction of the cassette. The distance metric may specify a likelihood that one or more of the junction epitopes spanning between a pair of adjacent epitopes will be presented.