Immutep S.A. announced the publication of a clinical research paper showing that its lead product, IMP321, given with first-line paclitaxel achieved clinical benefit in 90 per cent of metastatic breast carcinoma (MBC) patients. Correlations were observed with both the patients' monocyte (i.e. the primary target cell for IMP321) count before treatment and the degree of activation of monocytes during treatment.
The study was an open-label fixed-dose-escalation trial carried out in three cancer centers in the Paris region. The lead center was the René Huguenin Cancer Centre in Saint Cloud. The other centers were Tenon Hospital and the Georges Pompidou European Hospital in Paris. The immuno-monitoring was done by Immutep at its laboratories near Paris.
MBC patients were administered one dose of IMP321 s.c. every two weeks for a total of 24 weeks (12 injections). The repeated single doses were administered the day after chemotherapy at day 2 and day 16 of the 28-day cycles of paclitaxel (6 cycles). Blood samples were taken 13 days after the sixth and the twelfth IMP321 injections to determine sustained APC, NK and memory CD8 T cell responses. Thirty patients received IMP321 in three cohorts (doses: 0.25, 1.25 and 6.25 mg).
IMP321 induced both a sustained increase in the number and activation of APC (monocytes and dendritic cells) and an increase in the percentage of NK and long-lived cytotoxic effector-memory CD8 T cells. Clinical benefit was observed for 90 per cent of patients with only 3 progressors at 6 months. Also, the objective tumor response rate of 50 per cent compared favorably to the 25 per cent rate reported in the historical control group.
IMP321 is a recombinant soluble LAG-3Ig fusion protein that binds to MHC class II with high avidity and mediates APC and then antigen-experienced memory CD8
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