First-line chemoimmunotherapy in metastatic breast carcinoma: combination of paclitaxel and IMP321 (LAG-3Ig) enhances immune responses and antitumor activity.

BACKGROUND: 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+ T cell activation. We report clinical and biological results of a phase I/II in patients with metastatic breast carcinoma (MBC) receiving first-line paclitaxel weekly, 3 weeks out of 4. METHODS: 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 D2 and D16 of the 28-day cycles of paclitaxel (80 mg/m2 at D1, D8 and D15, for 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. RESULTS: Thirty MBC 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% of patients with only 3 progressors at 6 months. Also, the objective tumor response rate of 50% compared favorably to the 25% rate reported in the historical control group. CONCLUSIONS: The absence of toxicity and the demonstration of activity strongly support the future development of this agent for clinical use in combined first-line regimens. TRIAL REGISTRATION: ClinicalTrials.gov NCT00349934.

A phase I pharmacokinetic and biological correlative study of IMP321, a novel MHC class II agonist, in patients with advanced renal cell carcinoma.

PURPOSE: To evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of IMP321, a recombinant soluble LAG-3Ig fusion protein which agonizes MHC class II-driven dendritic cell activation. EXPERIMENTAL DESIGN: Patients with advanced renal cell carcinoma were treated with escalating doses of IMP321 s.c. Blood samples were assayed to determine plasma pharmacokinetic parameters, detect human anti-IMP321 antibody formation, and determine long-lived CD8 T cell responses. RESULTS: Twenty-one advanced renal cell carcinoma patients received 119 injections of IMP321 at doses ranging from 0.050 to 30 mg/injection s.c. biweekly for 6 injections. No clinically significant adverse events were observed. Good systemic exposure to the product was obtained following s.c. injections of doses above 6 mg. IMP321 induced both sustained CD8 T-cell activation and an increase in the percentage of long-lived effector-memory CD8 T cells in all patients at doses above 6 mg. Tumor growth was reduced and progression-free survival was better in those patients receiving higher doses (>6 mg) of IMP321: 7 of 8 evaluable patients treated at the higher doses experienced stable disease at 3 months compared with only 3 of 11 in the lower dose group (P = 0.015). CONCLUSION: The absence of toxicity and the demonstration of activity at doses above 6 mg warrant further disease-directed studies of IMP321 in combined regimens (e.g., chemoimmunotherapy).

A soluble form of lymphocyte activation gene-3 (IMP321) induces activation of a large range of human effector cytotoxic cells.

The principal antitumor immune response is mediated through the activation of type 1 cytotoxic (Tc1) CD8 T cells, NK cells, and monocytes/macrophages. In this study, we investigated the potency of a clinical-grade soluble form of lymphocyte activation gene-3 protein (IMP321), a physiological high-affinity MHC class II binder, at inducing in PBMCs an appropriate cytotoxic-type response in short-term ex vivo assays. We found that IMP321 binds to a minority (<10%) of MHC class II + cells in PBMCs, including all myeloid dendritic cells, and a small fraction of monocytes. Four hours after addition of IMP321 to PBMCs, these myeloid cells produce TNF-alpha and CCL4 as determined by intracellular staining. At 18 h, 1% of CD8+ T cells and 3.7% NK cells produce Tc1 cytokines such as IFN-gamma and/or TNF-alpha (mean values from 60 blood donors). Similar induction was observed in metastatic cancer patient PBMCs, but the values were lower for the NK cell subset. Early APC activation by IMP321 is needed for this Tc1-type activation because pure sorted CD8+ T cells could not be activated by IMP321. Only Ag-experienced, fully differentiated granzyme+ CD8 T cells (effector and effector memory but not naive or central memory T cells) are induced by IMP321 to full Tc1 activation. In contrast to IMP321, TLR1-9 agonists induce IL-10 and are therefore unable to induce this Tc1 IFN-gamma+ response. Thus, IMP321 has many properties that confirm its potential to be a new class of immunopotentiator in cancer patients.

IMP321 (sLAG-3) safety and T cell response potentiation using an influenza vaccine as a model antigen: a single-blind phase I study.

sLAG-3 (IMP321), a natural high affinity ligand for MHC class II, was tested for safety, tolerability and its ability to increase Th-1-type T cell responses to a commercial trivalent split influenza vaccine (Agrippal) in a phase I single-blinded, randomized, controlled clinical trial. Twenty healthy volunteers were first injected with increasing doses of IMP321 alone (safety for first-in-man use). Then 40 volunteers were recruited into 4 consecutive cohorts of 10 subjects, who were randomly assigned to receive the flu vaccine plus 3, 10, 30 or 100 microg IMP321 or the flu vaccine plus saline control. All vaccine formulations were found to be generally well tolerated with similar frequency and intensity of adverse reaction in groups receiving IMP321 as in controls. Post-vaccination humoral immune responses, as determined 29 and 57 days later by assay of hemagglutinin inhibition activity were similar for both IMP321 and control groups. In contrast, the addition of 10, 30 or 100 microg IMP321 to the flu vaccine resulted in higher levels of Th1-type (IFN-gamma, TNF-alpha or IL-2) flu-specific CD4 T cells in PBMC recovered at D29 and D57 and tested in a short-term ex vivo restimulation assay (6-colour FACS analysis after intra-cellular staining of cytokines). In summary, IMP321 as an adjuvant to a model antigen (Agrippal) was well-tolerated and may enhance T cell response vaccine immunogenicity.

IMP321 (sLAG-3), an immunopotentiator for T cell responses against a HBsAg antigen in healthy adults: a single blind randomised controlled phase I study.

BACKGROUND: LAG-3 (CD223) is a natural high affinity ligand for MHC class II. The soluble form (sLAG-3) induces maturation of monocyte-derived dendritic cells in vitro and is used as a potent Th1-like immune enhancer with many antigens in animal models. To extend this observation to human, a proof of concept study was conducted with a clinical-grade sLAG-3, termed IMP321, coinjected with alum-non-absorbed recombinant hepatitis B surface antigen. METHODS: In a randomised, single blind controlled phase I dose escalation study, 48 seronegative healthy volunteers aged 18-55 years were vaccinated at 0, 4 and 8 weeks by subcutaneous injection with 10 microg HBsAg mixed with saline (control) or with IMP321 at one of four doses (3, 10, 30 and 100 microg). To evaluate the efficacy of this three injections over 2 months immunization protocol, an additional control group was injected with the commercial vaccine Engerix-B. RESULTS: IMP321 was very well tolerated. Indeed, a lower incidence of adverse events was reported from the HBsAg plus IMP321 groups than from the Engerix-B group. HBsAg-specific antibody responses (anti-HBs) appeared sooner and were higher at 8 and 12 weeks in IMP321 recipients compared to HBsAg control subjects. More importantly, increased numbers of responders to HBsAg were found in IMP321 recipients compared HBsAg group, as revealed by higher post-vaccination frequencies of CD4 Th1 or CD8 Tc1 antigen specific T cells. IMP321 induced CD4 Th1 antigen-specific T cells in some of these naïve individuals after only one injection, especially in the 10 and 30 microg dose groups. CONCLUSION: IMP321 as an adjuvant to HBsAg was well-tolerated and enhanced T cell response vaccine immunogenicity (i.e. induced both CD4 Th1 and CD8 Tc1 antigen-specific T cells). This latter property has allowed the development of IMP321 as an immunopotentiator for therapeutic vaccines.