Can a pre-transplant drug help new marrow take hold?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Patients must voluntarily sign the informed consent form, be aged ≥18 years at the time of informed consent, and may be of either sex. 2. Diagnosed with myeloid neoplasms according to 2022 WHO diagnostic criteria 3. Bone marrow fibrosis grade ≥2 according to 2016 WHO myelofibrosis grading criteria 4. Undergoing first allogeneic hematopoietic stem cell transplantation 5. ECOG performance status: 0-2 6. Able to swallow tablets 7. Able to comply with study procedures and follow-up requirements Exclusion Criteria: 1. Currently receiving JAK inhibitors other than gecacitinib at screening (patients who have switched from other JAK inhibitors to gecacitinib before screening are eligible) 2. Prior allogeneic hematopoietic stem cell transplantation or organ transplantation 3. Uncontrolled severe infection, shock, severe organ failure, or any other condition that would preclude tolerance of the study treatment at enrollment. 4. Any significant clinical or laboratory abnormality that may affect safety evaluation, including: 1. Uncontrolled diabetes (fasting blood glucose \>13.9 mmol/L) 2. Uncontrolled hypertension despite ≥2 antihypertensive drugs (SBP ≥160 mmHg or DBP ≥100 mmHg) 3. Peripheral neuropathy (NCI-CTC AE v5.0 grade ≥2) 4. Serum creatinine \>1.5×ULN 5. ALT or AST \>2.5×ULN; DBIL or TBIL \>2.0×ULN 5. Any of the following within 6 months before screening: NYHA class III-IV congestive heart failure, unstable angina, myocardial infarction, cerebrovascular accident, or pulmonary embolism; arrhythmia requiring treatment; or QTcB \>480 ms. 6. Known active gastrointestinal ulcer at screening, or a history of gastrectomy or intestinal resection that may affect drug absorption. 7. Major surgery within 4 weeks before screening without full recovery 8. Known HIV infection and/or AIDS 9. History of tuberculosis infection 10. Epilepsy or use of psychotropic/sedative drugs at screening 11. Pregnant or breastfeeding women; patients unable to use effective contraception throughout the study period 12. Any other comorbidity that may affect the study or prior malignancy 13. Treatment with anticoagulant or antiplatelet drugs (except low molecular weight heparin) 14. Other severe conditions that, in the investigator's judgment, may affect patient safety or compliance 15. Known hypersensitivity to gecacitinib hydrochloride, drugs of the same class, or any excipients 16. Participation in other investigational drug or medical device clinical trials within 3 months before screening 17. Any comorbidity or prior malignancy that, in the investigator's judgment, may affect study participation, safety evaluation, or interpretation of study results.