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Sézary syndrome (SS) is a rare, aggressive leukemic form of cutaneous T-cell lymphoma characterized by generalized erythroderma, lymphadenopathy and circulating malignant CD4+ T cells (Sézary cells). Sézary syndrome evolves very quickly, patients are severely immunocompromised and their quality of life is drastically impaired. SS prognosis remains dismal despite recent therapeutic advances. AAC-11 (Anti-Apoptosis Clone 11, also known as Api5) is a survival scaffold protein that is widely expressed in cancer cells. Recent data indicate that AAC-11 might to be one of the central molecules involved in cancer cell progression and survival. Therefore, its inactivation might constitute an attractive approach for developing novel cancer therapeutics. AAC-11 contains a heptad leucine repeat domain that constitutes a protein-protein interaction motif, allowing its interaction with several apoptosis regulatory proteins. Loss-of-function mutations of the heptad leucine repeat motif are responsible for a defect in the interaction with its binding partners and associated with an abolition of the survival properties of AAC-11. We have recently described cell penetrating peptides based on the fusion of penetratin and a portion of the heptad leucine repeat region of AAC-11 that can induce cancer cells death. This effect is not observed in normal cells, suggesting high therapeutic indices. Here we evaluated the anti-tumor effect of a novel AAC-11-derived peptide, termed RT39, in the context of Sézary syndrome. Our results demonstrate that RT39 exerts an efficient and specific cytotoxic activity towards Sézary cells, while sparring the other immune cell populations, both ex vivo on primary patient cells and in vivo in preclinical Sézary syndrome murine models. Mechanistic studies revealed that RT39 induces membranolysis of Sézary cells by means of binding to p21-activated kinase 1 (PAK1) in the context of Sézary cells plasma membrane, where PAK1 is overexpressed. Preliminary pharmacokinetic studies in mice indicated that, after intravenous, subcutaneous or intraperitoneal administration, the half-life of the peptide is of the order of 30 minutes, but the elimination phase is very prolonged with high AUCs, indicative of durable exposure. Along with excellent tolerability in mice, our preclinical results support the development of RT39 as a new therapeutic strategy in Sézary syndrome. [ABSTRACT FROM AUTHOR]

gamma9delta2 T lymphocytes are non-conventional lymphocytes presenting a direct cytotoxic effect against a broad range of tumour targets. These cells also secrete inflammatory cytokines that can boost the other components of the immune system. In contrast to conventional CD8(+) T cells, the cytotoxic effect of gamma9delta2 T lymphocytes does not depend on the expression of major histocompatibility complex molecules by target tumour cells. INNACELL gammadeltatrade mark is a cell therapy product obtained by ex vivo amplification of mononuclear cells. The stimulation is achieved by a specific synthetic agonist of gamma9delta2 T lymphocytes, bromohydrin pyrophosphate (BrHPP). After a single stimulation with BrHPP, gamma9delta2 T lymphocytes are expanded for 2 weeks in a closed system in culture medium with interleukin-2 (IL-2). On day 15, cells are washed and harvested in 4% human serum albumin. In this manufacturing process, the total cell population is expanded by approximately 10-fold and gamma9delta2 T lymphocytes undergo a specific 1000-fold expansion, corresponding to a gamma9delta2 T lymphocyte enrichment of more than 70% at the end of the culture. This manufacturing process is much simpler than most current cellular therapy approaches using conventional CD8(+) T-cell lines or clones: there is no final or initial separation, no purification step and no use of feeder cells; the specific T-cell receptor-mediated signal provided by BrHPP is sufficient to trigger the IL-2-dependent expansion of the gamma9delta2 subset, which then becomes predominant in the cell culture in large amounts.

Vgamma9Vdelta2(+) cells represent the major population of gammadelta T cells in primate blood and react in an MHC-unrestricted fashion to a set of low m.w. nonpeptide phosphoantigens. Two types of structurally related agonists have been discovered so far: the natural phosphoantigens (hydroxydimethyl allyl-pyrophosphate or isopentenyl-pyrophosphate (IPP)) acting directly on Vgamma9Vdelta2(+) TCR and aminobisphosphonates, which block the mevalonate pathway in target cells, leading to accumulation of natural phosphoantigens that in turn activate Vgamma9Vdelta2(+) cells. We demonstrate in the cynomolgus monkey that Vgamma9Vdelta2 can be manipulated in vivo with bromohydrin pyrophosphate (BrHPP)/Phosphostim, a potent synthetic agonist for which the mechanism of action is similar to natural phosphoantigens. Although of very short half-life, injection of BrHPP leads to strong activation of Vgamma9Vdelta2, inducing production of a high level of Th1 cytokines. Combination of BrHPP with low-dose rhIL-2 induces specific amplification of effector-memory peripheral Vgamma9Vdelta2 in blood in a dose-dependant manner. This transient response returns to baseline within 10-15 days. Successive infusions of BrHPP and rhIL-2 induce less vigorous expansions, suggesting a progressive exhaustion of the response. As no toxicity is detected with or without IL-2, this scheme represents a promising immunotherapeutic strategy for induction of systemic Th1 cytokines and massive expansion of gammadelta T cell subset with antitumor and anti-infectious properties.