An Extension Study for Patients Previously Enrolled in Studies With Pelabresib

Inclusion Criteria: 1. Eligibility for Ongoing Pelabresib Treatment * Able to provide signed informed consent, agreeing to all protocol and ICF requirements. * At least 18 years old and legally able to consent in the study's jurisdiction. * Previously enrolled and currently receiving pelabresib in a parent study. * Demonstrating clinical benefit from pelabresib, as judged by the investigator. * Willing and able to follow all study visits, treatments, and procedures. * Agree to avoid pregnancy or fathering children: * Men: Must use highly effective contraception (≥99% effective) and avoid sperm donation from eligibility check through 94 days post-treatment. * Women of childbearing potential (WOCBP): Must test negative for pregnancy at eligibility, use highly effective contraception through 184 days post-treatment, undergo regular pregnancy testing, and avoid breastfeeding and oocyte donation during this period. * Women not of childbearing potential (surgically sterile or postmenopausal ≥12 months without other cause) are eligible. Note: Women with amenorrhea due to chemo/radiotherapy are considered WOCBP and must use contraception. 2. Eligibility for Survival Follow-up * Provide signed informed consent, agreeing to all protocol and ICF requirements. * Are at least 18 years old and legally able to consent. * Were previously enrolled in a pelabresib clinical study. * Are willing and able to comply with follow-up procedures. Exclusion Criteria: 1. Eligibility for Ongoing Pelabresib Treatment * Legally institutionalized or under judicial protection. * Enrolled in another interventional clinical trial (excluding the parent study). * History of hypersensitivity to pelabresib, its excipients, or similar drugs. * Significant gastrointestinal issues (e.g., active IBD, unresolved nausea/vomiting/diarrhea \> Grade 1) that may affect drug absorption. * Any medical condition deemed unsuitable by the investigator. * Uncontrolled illness or condition that may compromise safety or protocol compliance. * Received systemic anticancer or investigational treatment (excluding parent study drug or hormonal therapy) within 2 weeks or 5 half-lives before first dose. (Hydroxyurea/anagrelide allowed up to 24 hours prior.) * Received hematopoietic growth factors or androgenic steroids within 4 weeks before first dose. * Used strong CYP3A4 inhibitors/inducers (e.g., St. John's wort) within 2 weeks before first dose. Use during treatment is prohibited. * Female participants who are pregnant, breastfeeding, or not using required contraception. * Male participants who do not agree to use contraception or refrain from sperm donation as specified. * Unwilling or unable to comply with the study protocol. 2. Eligibility for Survival Follow-up • They are legally institutionalized or under judicial protection.