Results from a Phase IIa Study of the Anti-CXCL12 Spiegelmer Olaptesed Pegol (NOX-A12) in Combination with Bendamustine/Rituximab in Patients with Chronic Lymphocytic Leukemia

Background

Olaptesed pegol (NOX-A12) is a novel, potent, L-stereoisomer RNA aptamer that binds and neutralizes CXCL12/SDF-1, a chemokine which attracts and activates immune- and non-immune cells via interaction with the receptors CXCR4 and CXCR7. Signaling of CXCL12 is pivotal to the interactions of leukemic cells with bone marrow microenvironment. The therapeutic concept of olaptesed is to inhibit such tumor-supporting pathways and thereby mobilizing and sensitizing CLL cells to therapy.

Here we aim to assess the activity and safety of olaptesed in combination with bendamustine and rituximab (BR) in patients with relapsed / refractory CLL.

Methods

Twenty-eight relapsed or refractory CLL patients were enrolled and treated in this open-label, single-arm Phase IIa study. To investigate PK/PD, a pilot dose of 1 to 4 mg/kg olaptesed alone was administered to 3 patients per dose group (plus one additional replacement pt) before start of the regular treatment regimen (pilot group). Patients were treated using a dose titration design with intravenous (IV) olaptesed at doses increasing from 1 mg/kg to 2 mg/kg and 4 mg/kg at cycles 1, 2 and 3, respectively, at 1 hour before rituximab treatment. During cycles 4 to 6, olaptesed was dosed at the highest individually titrated dose. Rituximab was administered IV at doses of 375 mg/m² on day 1 of the 1^st28-day cycle and 500 mg/m² on day 1 of subsequent cycles. Bendamustine (70 - 100 mg/m²) was given IV on days 2-3 (cycle 1) or days 1-2 (cycles 2-6) of each 28-day cycle following administration of rituximab. Clinical response was assessed according to NCI-WG Guidelines (Hallek M et al. Blood 111; 2008: 5446-56).

Results

To date, 24 patients completed treatment (12 women, 12 men) with a median age of 68.5 years (range 52 to 79). At screening 5, 9 and 10 patients presented with Binet stage A, B and C, respectively. The median number of prior treatment lines was 1 (range 1-2). Seven high-risk patients presented an unfavorable disease state being relapsed within 24 months after fludarabine/bendamustine treatment (5 pts) and/or presenting a deletion/mutation of the TP53 gene (3 pts). Most patients (19 of 24) were previously treated with fludarabine or bendamustine.

A flow cytometric analysis of CD19⁺/CD5⁺CLL cells showed a rapid mobilization into the peripheral blood by a single dose of olaptesed which lasted throughout the observational time of 72h. Interestingly, CXCR4 expression levels increased on CLL cell surface in the periphery after olaptesed treatment. This increase, which peaked at 24h, likely reflects the extended circulation of CLL cells in the periphery due to the sustained blockade of CXCL12 by olaptesed. Reduction of lymphadenopathy by ≥ 50% was achieved in 14 out of 21 evaluable patients with reported enlarged lymph nodes by the end of treatment. Concomitantly, rapid reduction of lymphocytosis in peripheral blood with normalization by treatment cycle 2 – 3 was observed and the CLL to leukocyte ratio significantly improved.

Efficacy was assessed at the end of cycles 3 and 6. In the full-analysis-set, which excludes two non-evaluable patients (drop-out after the 1^st cycle due to adverse events), the overall response rate was 96%: Three patients (14%) achieved a complete response at end of cycle 6 (2 confirmed, 1 investigator reported) and eighteen patients (82%) achieved a partial response (fifteen at end of cycle 6 and three at end of cycle 3). Notably, all seven high-risk patients (defined as relapsed within 24 months after fludarabine/bendamustine treatment and/or presenting a deletion/mutation of the TP53 gene) responded to treatment with olaptesed + BR with a partial response. One patient had a progressive disease. Olaptesed at 1, 2 and 4 mg/kg at a single dose and in combination with BR was safe and well tolerated. The observed adverse reactions were qualitatively and quantitatively as expected for patients treated with BR.

Conclusion

Olaptesed in combination with BR was safe and well tolerated. Compared with historical data, olaptesed showed superiority over baseline therapy with regards to overall response rate and increasing rates of complete remission, warranting further development of this Spiegelmer in CLL.