TransCon IL-2 ß/γ: a novel long-acting prodrug with sustained release of an IL-2Rß/γ-selective IL-2 variant with improved pharmacokinetics and potent activation of cytotoxic immune cells for the treatment of cancer.

BACKGROUND: Recombinant interleukin-2 (IL-2, aldesleukin) is an approved cancer immunotherapy but causes severe toxicities including cytokine storm and vascular leak syndrome (VLS). IL-2 promotes antitumor function of IL-2Rß/γ+ natural killer (NK) cells and CD8+, CD4+ and gamma delta (γδ) T cells. However, IL-2 also potently activates immunosuppressive IL-2Rα+ regulatory T cells (Tregs) and IL-2Rα+ eosinophils and endothelial cells, which may promote VLS. Aldesleukin is rapidly cleared requiring frequent dosing, resulting in high Cmax likely potentiating toxicity. Thus, IL-2 cancer immunotherapy has two critical drawbacks: potent activation of undesired IL-2Rα+ cells and suboptimal pharmacokinetics with high Cmax and short half-life. METHODS: TransCon IL-2 ß/γ was designed to optimally address these drawbacks. To abolish IL-2Rα binding yet retain strong IL-2Rß/γ activity, IL-2 ß/γ was created by permanently attaching a small methoxy polyethylene glycol (mPEG) moiety in the IL-2Rα binding site. To improve pharmacokinetics, IL-2 ß/γ was transiently attached to a 40 kDa mPEG carrier via a TransCon (transient conjugation) linker creating a prodrug, TransCon IL-2 ß/γ, with sustained release of IL-2 ß/γ. IL-2 ß/γ was characterized in binding and primary cell assays while TransCon IL-2 ß/γ was studied in tumor-bearing mice and cynomolgus monkeys. RESULTS: IL-2 ß/γ demonstrated selective and potent human IL-2Rß/γ binding and activation without IL-2Rα interactions. TransCon IL-2 ß/γ showed slow-release pharmacokinetics with a low Cmax and a long (>30 hours) effective half-life for IL-2 ß/γ in monkeys. In mouse tumor models, TransCon IL-2 ß/γ promoted CD8+ T cell and NK cell activation and antitumor activity. In monkeys, TransCon IL-2 ß/γ induced robust activation and expansion of CD8+ T cells, NK cells and γδ T cells, relative to CD4+ T cells, Tregs and eosinophils, with no evidence of cytokine storm or VLS. Similarly, IL-2 ß/γ enhanced proliferation and cytotoxicity of primary human CD8+ T cells, NK cells and γδ T cells. SUMMARY: TransCon IL-2 ß/γ is a novel long-acting prodrug with sustained release of an IL-2Rß/γ-selective IL-2. It has remarkable and durable pharmacodynamic effects in monkeys and potential for improved clinical efficacy and tolerability compared with aldesleukin. TransCon IL-2 ß/γ is currently being evaluated in a Phase 1/2 clinical trial (NCT05081609).

TransCon CNP, a Sustained-Release C-Type Natriuretic Peptide Prodrug, a Potentially Safe and Efficacious New Therapeutic Modality for the Treatment of Comorbidities Associated with Fibroblast Growth Factor Receptor 3-Related Skeletal Dysplasias.

TransCon CNP is a C-type natriuretic peptide (CNP-38) conjugated via a cleavable linker to a polyethylene glycol carrier molecule, designed to provide sustained systemic CNP levels upon weekly subcutaneous administration. TransCon CNP is in clinical development for the treatment of comorbidities associated with achondroplasia. In both mice and cynomolgus monkeys, sustained exposure to CNP via TransCon CNP was more efficacious in stimulating bone growth than intermittent CNP exposure. TransCon CNP was well tolerated with no adverse cardiovascular effects observed at exposure levels exceeding the expected clinical therapeutic exposure. At equivalent dose levels, reductions in blood pressure and/or an increase in heart rate were seen following single subcutaneous injections of the unconjugated CNP-38 molecule or a daily CNP-39 molecule (same amino acid sequence as Vosoritide, USAN:INN). The half-life of the daily CNP-39 molecule in cynomolgus monkey was estimated to be 20 minutes, compared with 90 hours for CNP-38, released from TransCon CNP. C max for the CNP-39 molecule (20 µg/kg) was approximately 100-fold higher, compared with the peak CNP level associated with administration of 100 µg/kg CNP as TransCon CNP. Furthermore, CNP exposure for the daily CNP-39 molecule was only evident for up to 2 hours postdose (lower limit of quantification 37 pmol/l), whereas TransCon CNP gave rise to systemic exposure to CNP-38 for at least 7 days postdose. The prolonged CNP exposure and associated hemodynamically safe peak serum concentrations associated with TransCon CNP administration are suggested to improve efficacy, compared with short-lived CNP molecules, due to better therapeutic drug coverage and decreased risk of hypotension. SIGNIFICANCE STATEMENT: The hormone C-type natriuretic peptide (CNP) is in clinical development for the treatment of comorbidities associated with achondroplasia, the most common form of human dwarfism. The TransCon Technology was used to design TransCon CNP, a prodrug that slowly releases active CNP in the body over several days. Preclinical data show great promise for TransCon CNP to be an effective and well-tolerated drug that provides sustained levels of CNP in a convenient once-weekly dose, while avoiding high systemic CNP bolus concentrations that can induce cardiovascular side effects.