MYC targeting by OMO-103 in solid tumors: a phase 1 trial

Among the 'most wanted' targets in cancer therapy is the oncogene MYC, which coordinates key transcriptional programs in tumor development and maintenance. It has, however, long been considered undruggable. OMO-103 is a MYC inhibitor consisting of a 91-amino acid miniprotein. Here we present results from a phase 1 study of OMO-103 in advanced solid tumors, established to examine safety and tolerability as primary outcomes and pharmacokinetics, recommended phase 2 dose and preliminary signs of activity as secondary ones. A classical 3 + 3 design was used for dose escalation of weekly intravenous, single-agent OMO-103 administration in 21-day cycles, encompassing six dose levels (DLs). A total of 22 patients were enrolled, with treatment maintained until disease progression. The most common adverse events were grade 1 infusion-related reactions, occurring in ten patients. One dose-limiting toxicity occurred at DL5. Pharmacokinetics showed nonlinearity, with tissue saturation signs at DL5 and a terminal half-life in serum of 40 h. Of the 19 patients evaluable for response, 12 reached the predefined 9-week time point for assessment of drug antitumor activity, eight of those showing stable disease by computed tomography. One patient defined as stable disease by response evaluation criteria in solid tumors showed a 49% reduction in total tumor volume at best response. Transcriptomic analysis supported target engagement in tumor biopsies. In addition, we identified soluble factors that are potential pharmacodynamic and predictive response markers. Based on all these data, the recommended phase 2 dose was determined as DL5 (6.48 mg kg-1).ClinicalTrials.gov identifier: NCT04808362 .

Genetic and Pharmacological Blockade of Sigma-1 Receptors Attenuates Inflammation-Associated Hypersensitivity during Acute Colitis in CD1 Mice

Sigma-1 receptors (σ1Rs) are implicated in nociception, including pain sensitization, and inflammation. We assessed the role of σ1Rs on acute colitis-associated hypersensitivity using both genetic (constitutive knockout) and pharmacological blockade of the receptor. Colitis was induced in CD1 wild-type (WT) and σ1R KO mice (exposure to dextran sodium sulfate, 3%). A von Frey test was used to assess referred mechanosensitivity (abdominal and plantar withdrawal responses). The effects of the selective σ1R antagonists BD1063 and E-52862 were also assessed in WT animals. The expression of immune and sensory-related markers (RT-qPCR, Western blot) was assessed in the colon and lumbosacral spinal cord. The genetic ablation or pharmacological blockade of σ1Rs attenuated acute colonic inflammation in a similar manner. Mechanosensitivity was similar in WT and σ1R KO mice before colitis. In WT mice, but not in σ1R KO, colitis was associated with the development of referred mechanical hypersensitivity, manifested as a reduction in the withdrawal thresholds to mechanical probing (paw and abdominal wall). In WT mice, BD1063 and E-52862 blocked colitis-associated hypersensitivity. A genotype- and treatment-related differential regulation of sensory-related markers was detected locally (colon) and within the spinal cord. σ1Rs are involved in the development of acute intestinal inflammation and its associated referred mechanical hypersensitivity. The selective modulation of sensory-related pathways within the colon and spinal cord might be part of the underlying mechanisms. These observations support the pharmacological use of σ1R antagonists for the treatment of intestinal inflammation-induced hypersensitivity.

Abstract 3435: Identification of potential biomarkers of response to OMO-103, a first-in-modality pan-MYC inhibitor, in patients with advanced solid tumors

Background: MYC is a key transcription factor driving and maintaining human tumors. Since MYC has long been perceived as an “undruggable” target, to date, there is still no MYC inhibitor approved for clinical use. However, we designed and validated Omomyc, a MYC dominant negative mini-protein, demonstrating its potent therapeutic impact in various mouse models of cancer. Importantly, a Phase 1 study testing OMO-103, an Omomyc-based mini-protein developed by Peptomyc S.L., was successfully completed in 2022. Here, we present the main findings of the study and associated biomarker program.

Material and Methods: A phase I dose escalation study was performed in all-comers solid tumor patients, with a 3+3 design of 6 dose levels ranging from 0.48 to 9.72mg/kg, as a weekly 30-min i.v. infusion. Tumor and liquid biopsies were collected at screening, upon and at the end of treatment, to assess different biomarkers of drug activity.

Results: 22 patients with advanced solid tumors were included and 18 patients were considered evaluable for response by CT scan. Of these, 9 achieved SD. The PK analysis revealed a plasma half-life of >40h. No ADAs were detected in any of the patients. Drug pharmacodynamics supported target engagement, as demonstrated by Digital Spatial Profiling analysis showing shut down of MYC transcriptional signature in patients’ tumor biopsies. In addition, a distinctive pharmacodynamic cytokine signature that correlated with stable disease was found through liquid biopsies already 3 to 4 weeks before CT scan. Importantly, a cytokine signature was also identified as being predictive of disease stabilization at baseline and could help stratify patients in upcoming additional clinical studies. Finally, several anti-tumor immune related markers were also found modulated upon OMO-103 treatment.

Conclusion: OMO-103 demonstrates a favorable safety profile, with encouraging signs of activity supported by predictive and pharmacodynamic biomarkers worthy of further investigation.

Citation Format: Marie-Eve Beaulieu, Elena Garralda, Sílvia Casacuberta-Serra, Sandra Sandra Martínez-Martín, Emiliano Calvo, Víctor Moreno, Sergio López-Estévez, Laia Foradada, Guzman Alonso, Elena Corral, Bernard Doger, Tatiana Hernández, Judit Grueso, Íñigo Íñigo González-Larreategui, Erika Serrano del Pozo, Hugo Thabussot, Virginia Castillo Cano, Mariano F. Mariano F. Zacarías-Fluck, Jastrinjan Kaur, Fabio Giuntini, Jonathan R. Whitfield, Josefa Morales, Manuela Niewel, Laura Soucek. Identification of potential biomarkers of response to OMO-103, a first-in-modality pan-MYC inhibitor, in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3435.

Pharmacokinetic Analysis of Omomyc Shows Lasting Structural Integrity and Long Terminal Half-Life in Tumor Tissue

MYC is an oncoprotein causally involved in the majority of human cancers and a most wanted target for cancer treatment. Omomyc is the best-characterized MYC dominant negative to date. In the last years, it has been developed into a therapeutic miniprotein for solid tumor treatment and recently reached clinical stage. However, since the in vivo stability of therapeutic proteins, especially within the tumor vicinity, can be affected by proteolytic degradation, the perception of Omomyc as a valid therapeutic agent has been often questioned. In this study, we used a mass spectrometry approach to evaluate the stability of Omomyc in tumor biopsies from murine xenografts following its intravenous administration. Our data strongly support that the integrity of the functional domains of Omomyc (DNA binding and dimerization region) remains preserved in the tumor tissue for at least 72 hours following administration and that the protein shows superior pharmacokinetics in the tumor compartment compared with blood serum.

MYC Inhibition Halts Metastatic Breast Cancer Progression by Blocking Growth, Invasion, and Seeding

MYC's role in promoting tumorigenesis is beyond doubt, but its function in the metastatic process is still controversial. Omomyc is a MYC dominant negative that has shown potent antitumor activity in multiple cancer cell lines and mouse models, regardless of their tissue of origin or driver mutations, by impacting on several of the hallmarks of cancer. However, its therapeutic efficacy against metastasis has not been elucidated yet. Here we demonstrate for the first time that MYC inhibition by transgenic Omomyc is efficacious against all breast cancer molecular subtypes, including triple-negative breast cancer, where it displays potent antimetastatic properties both in vitro and in vivo. Importantly, pharmacologic treatment with the recombinantly produced Omomyc miniprotein, recently entering a clinical trial in solid tumors, recapitulates several key features of expression of the Omomyc transgene, confirming its clinical applicability to metastatic breast cancer, including advanced triple-negative breast cancer, a disease in urgent need of better therapeutic options.

Significance

While MYC role in metastasis has been long controversial, this manuscript demonstrates that MYC inhibition by either transgenic expression or pharmacologic use of the recombinantly produced Omomyc miniprotein exerts antitumor and antimetastatic activity in breast cancer models in vitro and in vivo, suggesting its clinical applicability.

Intestinal inflammation-associated hypersensitivity is attenuated in a DSS model of colitis in Sigma-1 knockout C57BL/6 mice

Sigma-1 receptors (σ1R) have been implicated in several pain pathways. We assessed the implication of σ1Rs in the development of intestinal inflammation and inflammation-associated referred hypersensitivity in a model of colitis in σ1R knockout (KO) mice. Colitis was induced with dextran sulfate sodium (DSS) in wild type (WT) and σ1R KO mice. The development of referred mechanical hypersensitivity (von Frey test) was assessed. Colonic and spinal changes in expression of immune- and sensory-related markers were also investigated (RT-qPCR/Western blot). Absence of σ1Rs had little impact in colitis generation and progression, although during the chronic phase a reduction in edema and a down-regulation of iNOS gene expression was observed. In σ1R KO mice, inflammation-associated hypersensitivity was significantly attenuated (paw) or completely prevented (abdomen). During colitis, in WT mice, changes in the colonic expression of nociceptive markers were observed during the acute and chronic phases of inflammation. Although σ1R KO mice showed similar regulation in the acute phase, an attenuated response was observed during the chronic phase of colitis. These differences were especially relevant for CB2 and TRPV1 receptors, which could play an important role in σ1-mediated regulation of sensitivity. No changes were detected on ERK phosphorylation at the level of the lumbosacral spinal cord. In summary, intestinal inflammation-associated referred hyperalgesia was reduced (paw) or absent (abdomen) in σ1R KO mice, thus confirming an important role for σ1R in the development of colitis-associated hypersensitivity. These results identify σ1Rs as a possible therapeutic target for the treatment of hypersensitivity associated to intestinal inflammation.

The Wnt signaling receptor Fzd9 is essential for Myc-driven tumorigenesis in pancreatic islets

The huge cadre of genes regulated by Myc has obstructed the identification of critical effectors that are essential for Myc-driven tumorigenesis. Here, we describe how only the lack of the receptor Fzd9, previously identified as a Myc transcriptional target, impairs sustained tumor expansion and β-cell dedifferentiation in a mouse model of Myc-driven insulinoma, allows pancreatic islets to maintain their physiological structure and affects Myc-related global gene expression. Importantly, Wnt signaling inhibition in Fzd9-competent mice largely recapitulates the suppression of proliferation caused by Fzd9 deficiency upon Myc activation. Together, our results indicate that the Wnt signaling receptor Fzd9 is essential for Myc-induced tumorigenesis in pancreatic islets.

Myeloid-derived suppressor cells expressing a self-antigen ameliorate experimental autoimmune encephalomyelitis

Previous work by our group showed that transferring bone marrow cells transduced with a self-antigen induced immune tolerance and ameliorated experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS). We also found that following retroviral transduction of murine bone marrow (BM) cells, the majority of cells generated and transduced were myeloid-derived suppressor cells (MDSCs). Here, we aimed to determine whether purified antigen-expressing MDSCs have similar therapeutic effects than those of unfractionated BM, and to investigate their potential mechanisms. We performed phenotypic and functional analyses in these cells using the same animal model, and we used purified antigen-expressing MDSCs in preventive and therapeutic approaches. These cells exerted therapeutic effects similar to those of BM cells, which depended upon self-antigen expression. The majority of monocytic (M)-MDSCs expressed the immunosuppressive molecule programmed death ligand-1 (PD-L1), CD80, CD86 and MHC class II molecules. Additionally, the animals infused with antigen-expressing cells exhibited lower percentages of activated T cells and higher percentages of B cells with a regulatory phenotype (B220⁺CD1d^high CD5⁺) in the spleen than their respective controls. MDSCs expressing self-antigens, alloantigens or therapeutic transgenes are tolerogenic and can be exploited therapeutically in autoimmune diseases, transplantation and in gene therapy, respectively.