This is a small-scale micro-randomized clinical trial of a new mobile just-in-time adaptive intervention (JITAI) designed to promote oral chemotherapy adherence in adolescents and young adults (AYA) with acute lymphoblastic leukemia (ALL). The goals of this study are to determine intervention feasibility and acceptability.

This is two-month study involving a 28-day run-in period (no intervention), followed by a 28-day micro-randomized pilot trial (i.e., a sequential factorial design) of a just-in-time adaptive intervention (JITAI) called ADAPTS (ADherence Assessments and Personalized Timely Support). ADAPTS is an app that integrates contextually-tailored mobile messages designed to promote adherence to an oral chemotherapy called 6-mercaptopurine (6-MP). Participants in the study will electronically-monitor 6-MP adherence with eCAPs for 28 days (approximately one month to establish baseline adherence before introducing the intervention). On approximately Day 29, they will download and use the app while continuing to monitor their adherence for the next 28 days. ADAPTS is an app that is available for Android and Apple devices, and has an Adolescent/Young Adult (AYA) version (i.e., the primary user) and a Caregiver version. ADAPTS delivers ecological momentary assessment (EMA) surveys each afternoon to AYAs and caregivers, at the same time prior to the evening 6-MP dose, for the 28-day period. Based on EMA responses, ADAPTS sends contextually-tailored mobile messages to AYAs (e.g., based on self-reported fatigue, mood) and objective data (e.g., weekend vs. weekday). After receiving a contextually-tailored message, AYAs will be asked to acknowledge receipt of the message by pressing a "thumbs up" or "thumbs down" button, to indicate whether or not they liked the message, or a "snooze" button indicating that it was not a good time to receive the message. Some features in ADAPTS are designed for AYAs and their caregivers to use together, such as a medication calendar that syncs with the eCAP and can be viewed by both members of the dyad. Following the 28-day intervention period, eCAPS will be returned and downloaded during the clinic appointment. AYAs and caregivers will complete a brief acceptability survey electronically via REDCAP, rating ADAPTS on a 5-point Likert scale to assess satisfaction, perceived appropriateness, perceive positive effects, perceived demands, and potential for future use. Exit interviews will also be conducted, audio-recorded, and transcribed to further assess acceptability. For feasibility, the following variables will be tracked: (1) screening rates, (2) recruitment rates, (3) % acknowledged micro-randomized messages, (4) technical difficulties (e.g., micro-randomized messages received when intended), (5) retention rates, and (6) completed assessments (EMA, eCAPS, post-measures).

AYA Inclusion Criteria:

• Ages 14-29
• Diagnosed with acute lymphoblastic leukemia (ALL) or lymphoma
• In the maintenance phase, completed at least one cycle and has at least one month of maintenance therapy remaining.
• Prescribed 6-mercaptopurine (6MP)
• English language proficiency
• For AYA <18, must have informed consent from their caregiver.

AYA Exclusion Criteria:

• Cognitive impairments that would limit ability to complete measures, determined by the medical team
• Absence of inclusion criteria above.

Caregiver Inclusion Criteria:

• Nominated by the AYA as a primary caregiver involved in cancer care (can be a parent, relative, partner, friend)
• English language proficiency

Caregiver Exclusion Criteria:

- Absence of inclusion criteria above.