Penfluridol for Relapsed/Refractory Small Cell Cancers

"Intervention: Penfluridol, an oral antipsychotic drug, is used as monotherapy. It targets DRD2, inhibits glycolysis, and induces apoptosis.~Dosing Schedule:~Phase Ib: 3+3 dose-escalation design. Initial dose 20 mg weekly, escalating to 40 mg, then 60 mg until recommended Phase II dose (RP2D) is determined based on 21-day DLT assessment.~Phase II: Expansion cohort at RP2D to further evaluate safety and estimate ORR. Duration: Treatment continues until progression, unacceptable toxicity, withdrawal, or investigator decision.~Monitoring: Regular AE/SAE monitoring using NCI-CTCAE v5.0. Assessments include weekly vital signs, biweekly blood tests, and ECGs every 2 weeks. Tumor response evaluated by RECIST 1.1 criteria with imaging every 2-3 cycles.~Dose Modification: Adjustments made for EPS, QTc prolongation, and proteinuria. Rationale for Single-Arm Design: Chosen due to the ultra-rare patient population and lack of established comparators. Efficient for determining RP2D and ORR."