Tumor-targeted antibody-cytokine fusion proteins, known as immunocytokines (ICKs) have potent antitumor activity in several preclinical tumor models. We have engineered an anti-CD20-interleukin 2 (IL-2) ICK based on the Leu16 anti-CD20 antibody with de-immunized variable (V) region and junction between the heavy (H) chain constant region and IL-2 (DI-Leu16-IL2). In-vitro studies of DI-Leu16-IL2 have demonstrated CD20 targeting, IL2 bioactivities, and antibody-dependent cell-mediated cytotoxicity (ADCC) functions. In a SCID mouse model, DI-Leu16-IL2 showed superior anti-lymphoma effects over rituximab or rituximab combined with systemic IL-2.
We have initiated a pilot trial of DI-Leu16-IL20 in CD20+ B-cell non-Hodgkin lymphoma (NHL) under an IRB-approved protocol (clinicaltrials.gov: NCT00720135). A total of 7 patients have been treated with DI-Leu16-IL20 at 0.5mg/m2. The first 2 cases received DI-Leu16-IL2 by intravenous infusion on days 2, 4 and 23, 25 after peripheral B cell depletion with low-dose rituximab (50mg/m2) on days 1 and 22. Five remaining patients received DI-Leu16-IL2 weekly for 4 weeks (days 2, 9, 16, 23) after B cell depletion with low-dose rituximab on days 1, 8, 15, and/or 22 as necessary, based on serum rituximab levels.
The treatment has been generally well tolerated with the majority of adverse events (AE) grade 1 or 2. Non-DLT grade 3 AE included one case of hyperglycemia, infection (herpes zoster), and prolonged QTc. One patient developed grade 3 hyponatremia, which was the only DLT in the study to date. One patient with diffuse large B cell NHL of the lower extremity achieved a CR after 2 cycles (significant PR after cycle 1; Figure 1). Another patient showed a temporal increase in FDG uptake on PET after cycle 1, which decreased after cycle 2 in 2 of the 3 responding lymph nodes, suggesting a local immunologic reaction with corresponding FDG uptake (immune-mediated FDG flare). A lymph node biopsy demonstrated a dense infiltration of T cells. One patient who had her residual tumor biopsied after DI-Leu16-IL2 treatment demonstrated loss of CD20 expression.
Pre-ICK B Cell Depletion and Pharmacologic Data: We have successfully maintained minimal or absent peripheral blood B cells, with a level-guided dosing of low-dose rituximab. The Cmax ranged between 75 and 125 ng/ml following each infusion of DI-Leu16-IL2. The half life was 6-8 hours and did not change significantly between doses. We have detected no anti-DI-Leu16-IL2 antibodies in any of the 7 patients treated on this protocol.
DI-Leu16-IL2 was highly immunologically active. There was a significant increase in local infiltrating T cells (predominantly CD8 T cells) in lymph node samples taken after DI-Leu16-IL2 in 3 of the 4 cases whose samples were available. Soluble IL2 receptor levels spiked with each DI-Leu16-IL2 infusion, up to 3 times above baseline. Among the cytokines and chemokines we evaluated using the Luminex platform, IL-5, IL-7, IL-10, IP10, IL-15, and IFN-gamma demonstrated high spikes (>2-fold increase) within 12 hours from each DI-Leu16-IL2 infusion, while IL-1, IL-12, MIG, TNF-alpha, IFN-alpha, and GCSF levels had a lesser degree of spikes (<2-fold increase). The data on the CR patient seem to show higher peak levels of IL15, IL7, and IP10, while MCP1, IL5, IL10, and MCP appeared lower compared with others. Flow cytometry-based cellular analyses showed no significant increase in regulatory T cells or myeloid-derived suppressor cells. Peripheral blood T cells were analyzed for TCR CDR3 sequence, and demonstrated oligoclonal T cell expansions, suggestive of antigen-driven T cell expansion.
This study demonstrated the clinical and immunologic data consistent with a proof-of-principle that DI-Leu16-IL2 is capable of inducing both local and systemic immune responses at a dose 0.5mg/m2, and was associated with a CR in a patient who had highly refractory NHL. A multi-center phase I trial of subcutaneously administered DI-Leu16-IL2 is currently underway.
Gillies: Provenance Biopharmaceuticals Corp (employment and equity ownership), Alopexx Oncology (Consultancy) : Consultancy, Employment, Equity Ownership.
Asterisk with author names denotes non-ASH members.