A Randomized, Phase II Study with Biomarker Analysis of Panobinostat with or without Rituximab in Relapsed Diffuse Large B Cell Lymphoma

INTRODUCTION: Novel therapies which consider the molecular diversity of diffuse large B cell lymphoma (DLBCL) are needed to salvage patients who fail to respond to standard chemoimmunotherapy. The majority of DLBCL contain mutations in histone modifying enzymes (HME) which suggests that histone deacetylase inhibitors (HDI) should be active. Preclinical data suggest that they also augment the effect of rituximab.

METHODS: In this randomized phase II study, we evaluated the response rate and toxicity of panobinostat, a pan-HDI, 30 mg orally 3 times a week, with or without rituximab, in 40 patients with relapsed and refractory DLBCL (median 3 prior regimens, range1-9). Tumors were sequenced for mutations known to be associated with DLBCL, and serial biopsies were analyzed for changes in biomarkers.

RESULTS: 21 patients were treated with panobinostat alone and 19 with panobinostat and rituximab. Overall, 12/40 patients (30%) responded to panobinostat (95% confidence interval 16.6%-46.5%) the addition of rituximab did not increase responses. The median duration of response was 14.5 months (95% confidence interval 9.4 to not reached) (Figure). At a median follow up of 17.5 months for responders, 6 of 12 patients have not progressed. Patients with dual expression of MYC and BCL2 (6/27) and those with FAS mutations (5/33) did not respond although responses were seen in 5/10 patients with TP53 mutations. Responses were seen in 8/24 patients with mutations in HME genes. Patients with MEF2B mutations had the greatest odds of response (P<0.05) and a higher number of HME mutations tended to increase the odds of response. Changes in histone H3 acetylation and MYC expression were observed but did not correlate with response.

CONCLUSION: Panobinostat induces durable responses in some patients with relapsed DLBCL, and accompanying biomarker analyses identified DLBCL subgroups likely to respond.

Figure 1.

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Progression free survival overall and for responders, N=40 patients.

Figure 1.

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Progression free survival overall and for responders, N=40 patients.

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