Phase I clinical trial on pomalidomide and dexamethasone in treating patients with relapsed/refractory primary central nervous system lymphoma (PCNSL) or primary vitreoretinal lymphoma (PVRL).

Abstract

7516 Background: PCNSL is a diffuse large B cell lymphoma confined to the CNS. Pomalidomide (POM) is a novel immunomodulatory agent with excellent CNS penetration (~40%) based on CNS PK analysis in rats and pre-clinical therapeutic activity against CNS lymphoma. Methods: A Phase I clinical trial was undertaken to determine the maximal tolerated dose (MTD) of POM, safety profile and overall response rate (ORR). Treatment consists of POM daily for 21 days every 28 days in combination with dexamethasone 40 mg PO weekly for two cycles followed by POM alone in subsequent cycles until progression or intolerance. 4 dose escalation levels of POM (3mg, 5mg, 7mg, and 10 mg) were planned. Thromboprophylaxis with oral anticoagulant or aspirin was required. MTD determination has been completed and expansion of the MTD cohort is ongoing. Therapeutic responses were evaluated per the international PCNSL collaborative group (IPCG) criteria after 2 cycles of treatment. The trial is registered with ClinicalTrials.gov (#NCT01722305). Results: 21 of 25 patients accrued were eligible for assessment. The MTD was determined to be 5 mg qd for 21 days every 28 days. Two DLTs were seen at dose level 3 (Grade 3 dyspnea and grade 4 thrombocytopenia). One DLT was seen in the expanded MTD cohort (Grade 4 neutropenia and lymphocytopenia). ORR for the study (9/21) was 43% (95% CI- 22%, 66%) with 4 CR, 1 CRu and 4 PR. 3 responders completed 2, 4, and 6 cycles before progression. 6 responders have completed 4, 5, 6, 10, 12, and 32 cycles and remain on treatment. ORR for the MTD dose level was (5/12) 42% (95% CI- 15%, 72%) with 3 CR and 2 PR. 2 patients had stable disease (SD). Pseudo-progression was seen in 1 patient. Overall, grade 3/4 toxicity was hematologic (neutropenia, anemia, and thrombocytopenia) in 38.1% and non-hematologic in 33.3% (fatigue, pneumonia, sepsis, syncope, dyspnea, hypoxia, respiratory failure and maculo-papular rash). Percent CSF/blood ratio of POM was determined to be 19% in 1 patient. Conclusions: Pomalidomide treatment is feasible with therapeutic activity against relapsed/refractory PCNSL and should be further developed. Clinical trial information: NCT01722305.