Ublituximab (TGTX-1101), a Novel, Third-Generation Anti-CD20 Antibody Demonstrates Enhanced Antitumor Activity Compared to Rituximab in Primary CNS and Intraocular Lymphoma Murine Models.

Primary Central Nervous lymphomas (PCNSL), that comprise primary cerebral lymphoma (PCL) and primary intraocular lymphoma (PIOL), are typically CD20⁺ diffuse large B-cell lymphomas that have no detectable disease outside the brain or eye. Rituximab (RTX), an anti-CD20 antibody, has demonstrated encouraging clinical benefit in systemic B-cell lymphomas as well as PCL and PIOL, however, the role of RTX in treatment of PCNSL/PIOL remains controversial, and these highly aggressive malignancies are often incurable with available therapies. Therefore, additional treatment options are needed. Ublituximab (UTX) is a novel, glycoengineered chimeric anti-CD20 monoclonal antibody (mAb) that has a high affinity for FcγRIIIa (CD16) receptors, and therefore greater ADCC activity than RTX (Le Garff-Tavernier et al., 2011). Herein, we assess the antitumor effects of UTX compared to RTX in murine models of PCL and PIOL.

The murine lymphoma B-cell line A20.IIA-GFP-hCD20 (H-2^d) was injected into the right cerebral striatum (PCL model) or the vitreous (PIOL model) of adult BALB/c mice (H-2^d); 7 days later, single doses of UTX were injected either into the tumor site intracerebrally (PCL) or intravitreously (PIOL), or at distance of the tumor site (intrathecally, PCL). RTX was used as a reference compound. Survival was monitored for injected mice for up to 100 days, and flow cytometric analyses were performed to assess tumor growth and T-cell infiltration.

In PCL and PIOL models, single doses of UTX had a marked antitumor effect more pronounced than that obtained with an equivalent dose of RTX. In the PCL model, there was an overall survival (OS) advantage with intracerebral injections of UTX compared to RTX (50% vs. 10%, n=10 in each group, p=0.0028). The reduction in tumor cells was correlated with an increased proportion of CD8⁺ T cells. Moreover, intrathecal injections of UTX increased OS compared to buffer solution. In the PIOL model, the absolute number of tumor cells analyzed 8 days after treatment had decreased more significantly (p=0.027) with UTX compared to the RTX group. This finding again confirmed the superiority of UTX in this setting.

These results confirm that the novel, third-generation mAb, UTX has a sustained and greater antitumor effect than RTX on primary cerebral and intraocular lymphomas when assessed in vivo. Additional experiments evaluating the combination of UTX + methotrexate are ongoing. Clinical trials to evaluate UTX as an innovative therapeutic approach to treat primary cerebral and intraocular B-cell lymphomas are currently being evaluated.

Jacquet:LFB Biotechnologies: Employment. Fridman:LFB Biotechnologies: Membership on an entity's Board of Directors or advisory committees. Sportelli:TG Therapeutics, Inc.: Employment, Equity Ownership. Urbain:LFB Biotechnologies: Employment.