SON-1210 - a novel bifunctional IL-12 / IL-15 fusion protein that improves cytokine half-life, targets tumors, and enhances therapeutic efficacy

Background

The potential synergy between interleukin-12 (IL-12) and IL-15 holds promise for more effective solid tumor immunotherapy. Nevertheless, previous clinical trials involving therapeutic cytokines have encountered obstacles such as short pharmacokinetics, limited tumor microenvironment (TME) targeting, and substantial systemic toxicity.

Methods

To address these challenges, we fused single-chain human IL-12 and native human IL-15 in cis onto a fully human albumin binding (FHAB) domain single-chain antibody fragment (scFv). This novel fusion protein, IL12-FHAB-IL15 (SON-1210), is anticipated to amplify the therapeutic impact of interleukins and combination immunotherapies in human TME. The molecule was studied in vitro and in animal models to assess its pharmacokinetics, potency, functional characteristics, safety, immune response, and efficacy.

Results

SON-1210 demonstrated robust binding affinity to albumin and exhibited the anticipated in vitro activity and tumor model efficacy that might be expected based on decades of research on native IL-12 and IL-15. Notably, in the B16F10 melanoma model (a non-immunogenic, relatively "cold" tumor), the murine counterpart of the construct, which had mouse (m) and human (h) cytokine sequences for the respective payloads (mIL12-FHAB-hIL15), outperformed equimolar doses of the co-administered native cytokines in a dose-dependent manner. A single dose caused a marked reduction in tumor growth that was concomitant with increased IFNγ levels; increased Th1, CTL, and activated NK cells; a shift in macrophages from the M2 to M1 phenotype; and a reduction in Treg cells. In addition, a repeat-dose non-human primate (NHP) toxicology study displayed excellent tolerability up to 62.5 µg/kg of SON-1210 administered three times, which was accompanied by the anticipated increases in IFNγ levels. Toxicokinetic analyses showed sustained serum levels of SON-1210, using a sandwich ELISA with anti-IL-15 for capture and biotinylated anti-IL-12 for detection, along with sustained IFNγ levels, indicating prolonged kinetics and biological activity.

Conclusion

Collectively, these findings support the suitability of SON-1210 for patient trials in terms of activity, efficacy, and safety, offering a promising opportunity for solid tumor immunotherapy. Linking cytokine payloads to a fully human albumin binding domain provides an indirect opportunity to target the TME using potent cytokines in cis that can redirect the immune response and control tumor growth.

Abstract 4229: An innovative human platform for targeted delivery of bispecific interleukins to tumors

Combination approaches using stimulatory cytokines, checkpoint inhibitors, chemotherapy and/or radiation therapy are known to improve overall survival of cancer patients. Recombinant interleukins (IL) have had limited clinical success due to short pharmacokinetics, inefficient tumor targeting and more frequent dosing, leading to toxicities. To address these issues, we have developed a novel platform that delivers immunomodulators in either a mono- or bispecific format. The platform consists of a fully human, albumin-binding scFv domain (FHAB) that provides an improved pharmacokinetic profile, enhanced tumor targeting by binding over-expressed FcRn, GP60 and SPARC, a dose-sparing effect that further decreases the toxicity risk, and a broader therapeutic index.

Interleukin-12, IL-15, and IL-18 are among the most potent inducers of anti-tumor activity and have been evaluated in numerous clinical studies. Sonnet's bispecific drug candidates are constructed with IL-12 on the FHAB platform, and include IL12-FHAB-IL15, GMcsf-FHAB-IL12, and IL18-FHAB-IL12. These bispecific molecules span a broad range of mechanisms of action that bridge innate and adaptive tumor immunity. They are produced in Chinese Hamster Ovary cells using an intensified perfusion manufacturing process that allows for rapid scale-up for commercial manufacturing.

The “cold” immunosuppressive B16-F10 melanoma tumor model was used for comparing the efficacy of the bispecific candidates administered in a single i.v. dose. All three constructs showed statistically significant tumor size reduction compared to placebo or native interleukin at a 5µg dose: 67% for IL12-FHAB-IL15, 37% for GMcsf-FHAB-IL12 and 76% for IL18-FHAB-IL12. At lower dose levels with nearly equivalent efficacy, mice showed no body weight loss and exhibited reduced toxicity with transient adverse reactions that resolved by Day 8.

Optimal synergistic efficacy occurred with the IL18-FHAB-IL12 bispecific. Interestingly, IL-18 upregulates the IL-12 receptor and vice versa. Further, IL-18 also increased levels of chemokines CXCL9 and CXCL10, which in turn resulted in significant increases in activated NK, NKT, Th1, and cytotoxic CD8 T cells, as well as an increase in M1 and decrease in M2 cells in the tumor vs. the spleen. This data points to the potential for changing immunologically “cold” tumors to clinically responsive “hot” ones.

In conclusion, these studies demonstrated that while the powerful anti-tumor effects of IL-12 are evident in the monospecific IL12-FHAB, in the bispecific format IL-12 can synergize with other cytokines e.g., IL-18 and GM-CSF, resulting in superior anti-tumor activity when compared to their monospecific modalities. Ongoing in vitro and in vivo studies will involve bispecific IL-FHAB constructs used with various checkpoint inhibitors to further improve the immune stimulation and anti-tumor activities of novel combination therapies.

Citation Format: John K. Cini, Stephen J. McAndrew, Nick Evans, Lucie Janeckova, Maryam Ahmadi, Rukiye-Nazan Eraslan, Miglena G. Prabagar, Susan Dexter, Richard T. Kenney. An innovative human platform for targeted delivery of bispecific interleukins to tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4229.

Biodegradable nanoparticles inhibit tumor growth by altering tumor-associated macrophages and cancer-associated fibroblasts

e14553

Background: The tumor microenvironment (TME) plays a crucial role in tumor growth and progression and has a significant influence on response to therapy. The TME consists of myeloid-derived cells, stroma (e.g. fibroblasts and extracellular matrix (ECM)), and the vasculature that together support tumor growth and progression. Studies in animal models and in humans show that myeloid- derived cells such as myeloid derived suppressor cells (MDSCs) and tumor associated macrophages (TAMs) engage in activities that support tumor growth and progression. These cells also promote immune suppression in the TME that blunts the efficacy of the anti-cancer drugs and immune-targeted therapies such as immune checkpoint inhibitors. In addition to MDSCs, cancer-associated fibroblasts (CAFs) in the TME support tumor progression via production of pro-tumor and pro-angiogenic growth-factors, remodeling of the ECM via production of proteases, and suppression of anti-tumor immune function. CAF abundance in the TME is a negative prognostic factor for several solid tumors and is associated with negative outcomes and poor response to immune-targeted therapies like immune checkpoint inhibitors. ONP-302 nanoparticles fabricated from biodegradable poly (lactic-co-glycolic acid)(PLGA) polymer have been previously described in the literature for the treatment of acute inflammatory conditions via immuno-modulatory effects on myeloid derived cells. Here, we evaluated the efficacy of ONP-302 nanoparticles at inhibiting tumor growth via targeted inhibition of myeloid-derived cells and reshaping of the TME. Methods: ONP-302 anti-tumor efficacy was evaluated in syngeneic mouse tumor models using both immunocompetent and immunodeficient mice. We examined the effect of ONP-302 treatment tumor growth kinetics and effects on the major cellular constituents of the TME such as myeloid-derived cells and CAFs. Results: Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. We found ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Conclusions: Our data indicate that the slowing of tumor growth after ONP-302 treatment is due to disruptions in known signaling pathways involving TAMs and CAFs, pathways typically supporting tumor growth. These data taken in concert indicate the activity of ONP-302 is pleotropic and affects multiple pathways.

ONP-302 Nanoparticles Inhibit Tumor Growth By Altering Tumor-Associated Macrophages And Cancer-Associated Fibroblasts

In this study, we evaluated the ability of negatively charged bio-degradable nanoparticles, ONP- 302, to inhibit tumor growth. Therapeutic treatment with ONP-302 in vivo resulted in a marked delay in tumor growth in three different syngeneic tumor models in immunocompetent mice. ONP- 302 efficacy persisted with depletion of CD8+ T cells in immunocompetent mice and also was effective in immune deficient mice. Examination of ONP-302 effects on components of the tumor microenvironment (TME) were explored. ONP-302 treatment caused a gene expression shift in TAMs toward the pro-inflammatory M1 type and substantially inhibited the expression of genes associated with the pro-tumorigenic function of CAFs. ONP-302 also induced apoptosis in CAFs in the TME. Together, these data support further development of ONP-302 as a novel first-in- class anti-cancer therapeutic that can be used as a single-agent as well as in combination therapies for the treatment of solid tumors due to its ability to modulate the TME.

Abstract 524: The novel STING agonist VB-85247 induces robust durable antitumor immune responses by intravesical administration in a non-muscle invasive bladder cancer model

Introduction: Bacillus Calmette-Guerin (BCG) unresponsive non-muscle invasive bladder cancer (NMIBC) patients are in great need of effective immunotherapies. STING (Stimulator of Interferon Genes) plays a central role in mounting innate and adaptive immune responses to tumor cells. Activation of the STING pathway leads to the induction of inflammatory cytokines (IFN-α/β, TNF-α, IL-6 and CXCL10), maturation and activation of dendritic cells (DC), and induction of anti-tumor T cells. Our group has developed a novel STING agonist, VB-85247. Here we use a murine NMIBC model to report the potent antitumor effect of VB-85247 compared to standard of care BCG and anti-PD1 checkpoint inhibitor therapy currently used in the management of NMIBC.

Methods: We developed a mouse model of Non-Muscle Invasive Bladder Cancer (NMIBC) utilizing orthotopically implanted MB49-Luc cells, permitting BLI (Bioluminescence) measurement of tumor growth by In Vivo Imaging Systems (IVIS).

Results: VB-85247 was found to bind to mouse STING and all major variants of human STING protein. VB-85247 induced high levels of IFN-β and other cytokines across cells from different species, including primary human bladder epithelial cells. VB-85247 treatment by intravesical instillation in the mouse model of NMIBC resulted in dose dependent tumor regression starting after the first treatment, achieving up to a 100% complete response rate at the 40 µg dose level after 5 weekly treatments. The treatment was well tolerated, eliciting strong and durable anti-tumor immune responses without any mortality. All cured mice rejected a re-challenge with MB49-Luc cells with no further treatment, demonstrating long-lasting anti-tumor immunity. By contrast, BCG treatment in the same model was not efficacious. Combination with anti-PD1 treatment reduced the dose of VB-85247 needed to achieve 100% complete responses to 20 µg, whereas anti-PD1 treatment alone resulted in only 25% complete responses. In addition, a single dose of 40 µg VB-85247 by bladder instillation in the NMIBC model induced systemic immune responses including serum cytokines demonstrating Type I IFN responses plus DC mobilization and activation in the blood, draining lymph nodes, and spleen within 24 hours.

Conclusions: The STING agonist VB-85247 was well tolerated and displayed robust efficacy by bladder instillation in a mouse orthotopic tumor model of NMIBC, achieving up to 100% complete responses. All cured mice rejected fresh inoculations of tumor cells with no further treatment, demonstrating induction of immunologic memory. Treatment with BCG was not efficacious in the model. These results suggest the potential utility of the VB-85247 STING agonist in the treatment of BCG unresponsive NMIBC patients. Based on these data, VB-85247 is being advanced to clinical development.

Citation Format: Miglena Prabagar, Venu Bommireddy, Rachael Siegel, Haihua Zheng, Lee Pellegrino, Stanley Nawoschik, Albert Uveges, Steven Paget, Ku Lu, Krista Saufler, Axel Metzger, David Diller, Jason Trama, Grant Gallagher, Chia-Yu Huang, Brian McGuinness, James R. Beasley, Michael McQueney, Martin Adelson, Gary L. Schieven, Eli Mordechai, Rukiye-Nazan Eraslan. The novel STING agonist VB-85247 induces robust durable antitumor immune responses by intravesical administration in a non-muscle invasive bladder cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 524.