Abstract 700: Development of a second-generation TRAIL agonist and predictive biomarker profile for colorectal cancer

In colorectal cancer (CRC), RAS mutated cancers comprise 30-50%, for which there are limited treatment options. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been found to selectively induce cell death in 50% of the CRC cell lines tested in vitro and this appears to be independent of RAS mutation status. Minimal clinical success was observed for first generation TRAIL receptor agonists primarily due to poor agonist activity and poor bioavailability. In addition, a biomarker to identify responsive patients was lacking. Here we present the therapeutic development of MM-201, a next generation TRAIL receptor agonist, and its companion biomarker strategy. MM-201 is composed of an IgG1 Fc fused to a single chain TRAIL trimer (Fc-scTRAIL) engineered for improved stability and activity. Using TRAIL surface display on yeast, we identified three mutations (R130G/N228S/I247V) from a random mutagenesis library that lead to enhanced surface expression and DR5 binding. Incorporation of these three mutations into each TRAIL protomer of MM-201 resulted in an improvement of greater than 10°C in TM and an extended serum half-life of 33 hours in mice compared to wild-type Fc-scTRAIL and comparable activity in a panel of colorectal cancer (CRC) cell lines. To uncover predictive biomarkers for MM-201, we used continuous logic gate analysis on a publicly available dataset of cell survival for 27 CRC cell lines treated with cross-linked TRAIL cytokine. Using this dataset and gene expression data from Cancer Cell Line Encyclopedia, we explored combinations of 33 differentially expressed genes in the apoptosis pathway and identified a two gene biomarker signature that positively correlated with TRAIL response in CRC cell lines. The combined signature of high DR4 and low cIAP-1 was identified with a correlation coefficient of 0.99 with MM-201 response across 15 CRC cell lines both in vitro and in vivo. Subsequently we evaluated MM-201 and our biomarker approach in vivo, in a group of five CRC patient-derived xenograft (PDX) models. Four of the five models were sensitive to MM-201, with an average tumor growth inhibition (TGI) of 91%. The relative expression of DR4 and cIAP-1 in each of the PDX models was measured by RT-qPCR and the biomarker scores were observed to be significantly higher for all responding models. Given the responses observed in preclinical models, we used TCGA data to assess biomarker prevalence in patient tumor tissues. This analysis predicted that 59% of samples would have a biomarker score greater than 0.5, which correlates to a 75% reduction in cell viability in vitro. In contrast, only 12% of normal tissues had a score in this range. Our biomarker signature identifies a potentially responsive patient population and when combined with our next generation TRAIL agonist, MM-201, has the potential for development in CRC, especially for RAS mutated cancers.

Citation Format: Sara Ghassemifar, Yasmin Hashambhoy-Ramsay, Haluk Yuzugullu, Tamara Utermark, Violette Paragas, Tim Maiwald, Lia Luus, Maja Razlog, Hannah Hudson, Diane Chai, Birgit Schoeberl, C. Patrick Reynolds, Peter Sorger, Andrew J. Sawyer, Daryl C. Drummond, Eric Tam. Development of a second-generation TRAIL agonist and predictive biomarker profile for colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 700.

Abstract 2491: Engineering and preclinical activity of MM-201, a best-in-class TRAIL receptor agonist

Early attempts at using TNF superfamily members for anticancer therapies, TNF and FAS, led to serious systemic toxicities. However, the discovery of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) introduced an agonist capable of killing tumor cells via apoptosis without the side effects observed with TNF and FAS agonists. First generation TRAIL agonists included a recombinant version of human TRAIL (dulanermin), as well as multiple DR4 and DR5 agonist antibodies. Despite some isolated responders, the initial clinical results were poor. The first-generation TRAIL agonists were limited by poor pharmacokinetics (the half-life for dulanermin was between 30 and 60 minutes) or by poor agonist activity and the need for Fc-mediated cross linking. Here we present the development and evaluation of two second generation TRAIL agonists, MM-201a and MM-201b. Both versions are composed of an IgG1 Fc fused to a single chain TRAIL trimer (Fc-scTRAIL). Mutations within the TRAIL domains, selected from a random mutagenesis library, were introduced to improve stability, expression, and DR5 binding. MM-201a has 5 mutations in each monomeric unit (R130G/N228S/I247V/Y213W/S215D) and MM-201b has 3 mutations in each monomer (R130G/N228S/I247V). In a panel of 27 colorectal carcinoma and sarcoma cell lines, both versions of MM-201 were observed to be significantly more active than all comparators, including the TRAIL cytokine and both DR4 and DR5 antibodies. MM-201a had a level of activity similar to ABBV-621, a single chain TRAIL fused to the N-terminus of an IgG1 Fc that is currently the subject of a Phase 1 trial. However, MM-201b was significantly more active than both MM-201a and ABBV-621, with up to 11-fold lower IC50 across a panel of 12 CRC cell lines. MM-201b treatment reduced cell viability to less than 20% in 10 out 12 colorectal cancer cell lines and in 8 of these cell lines, this was achieved at concentrations less than 1 nM. MM-201 also induced complete cell death at 1 nM or less in 3 of 8 synovial sarcoma and chondrosarcoma cell lines tested. For example, MM-201b reduced the viability of the SW-982 synovial sarcoma cell line to 17% at a dose of 1.5 pM, which is nearly twice the reduction in viability from the same dose of ABBV-621. We next evaluated both versions of MM-201 in multiple colorectal cancer and sarcoma patient-derived xenograft (PDX) models. In the Ewing’s sarcoma PDX model TM01617, MM-201b treatment resulted in 90% tumor growth inhibition. In the same model, treatment with 10 mg/kg docetaxel resulted in 73% growth inhibition; however, in combination with MM-201a, the same dose resulted in a 100% complete response rate. Similar results were observed in the SK-UT1 uterine sarcoma xenograft. Based on this evidence, we believe that MM-201b is best in class and, when combined with an appropriate patient selection strategy, has significant potential for the treatment of sarcomas and colorectal cancer in patients.

Citation Format: Andrew J. Sawyer, Sara Ghassemifar, Christina Wong, Jennifer Richards, Stephanie Grabow, James Suchy, Alexander Koshkaryev, Maja Razlog, Eric Tam, Daryl C. Drummond. Engineering and preclinical activity of MM-201, a best-in-class TRAIL receptor agonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2491.

Abstract P5-04-19: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Ghassemifar S, Finn G, Zhang H, Richardson J, Kuesters G, Santillana S, Pipas M. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-19.

Abstract 2716: Development of 4-1BB agonists: Ligand fusion shows greater anti-tumor activity than antibodies in vivo

Members of the tumor necrosis factor (TNF) superfamily of costimulatory receptors have emerged as promising targets for modulation of tumor infiltrating lymphocytes. Among these, 4-1BB (CD137) has a prominent role in promoting survival and expansion of cytotoxic CD8 T cells as well as activation of CD4 T cells, NK cells, and antigen presenting cells. The clinical relevance of 4-1BB agonism is currently being evaluated for two antibodies: urelumab (IgG4) and utomilumab (IgG2). However, it has been established that for the trimeric TNF receptor family, the homotrimeric ligands are superior activators compared to bivalent agonistic antibodies. Here we describe a prototype 4-1BB agonist consisting of three human 4-1BB ligands linked together as a single polypeptide chain and fused to the C-terminus of human IgG1 Fc (STIM-41BBL). Compared to a clinically relevant human 4-1BB antibody, STIM-41BBL shows increased activation of 4-1BB in a NF-kappa B reporter cell line. STIM-4-1BBL also shows augmented cytokine release compared to the antibody in CD8 T cells. Furthermore, we have developed a mouse STIM-41BBL and like the human counterpart, the ligand fusion induced greater cytokine release than an agonistic mouse 4-1BB antibody (IgG2a) in CD8 T cells. We have also introduced mutations (D265A/N297A) to the mouse 4-1BB antibody to make it effectorless in order to better approximate the clinical 4-1BB antibodies. Subsequently, we demonstrate that the murine STIM-41BBL had greater anti-tumor activity than the 4-1BB antibody in a MC38 tumor model. These results support the continued development of a 4-1BB ligand based therapeutic and suggests the greater potential of a STIM-41BBL fusion to a targeting antibody for more precise activation of immune system.

Citation Format: Eric Tam, Galina Craig, Sara Ghassemifar, Alexander Koshkaryev, Sara Movassaghian, Cormac Cosgrove, James Sampson, Daryl Drummond, Andreas Raue. Development of 4-1BB agonists: Ligand fusion shows greater anti-tumor activity than antibodies in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2716.

Abstract 22: MM-161, a first-in-class pan-FGFR antibody

Aberrant signaling of the FGFR pathway has long been known to promote tumorigenesis and angiogenesis across multiple cancer indications. However, the development of an effective and well-tolerated FGFR targeted inhibitor has been hindered by the need to block the activation of multiple mitogenic receptors while avoiding significant toxicities associated with blocking endocrine FGF ligands.

Here we disclose for the first time a novel FGFR targeted antibody, MM-161, designed to block ligand-dependent signaling driven by all four FGF receptors, specifically the IIIc-isoforms. MM-161 is well tolerated in mice and cynomolgus monkeys with no significant weight loss observed in either species. Efficacy studies demonstrated that MM-161 monotherapy leads to significant tumor growth inhibition or tumor regression of xenografts of human lung, renal and endometrial cancer amongst others. Importantly, MM-161 has a dual mechanism of action by inhibiting both proliferation and angiogenesis. We will present data illustrating that inhibition of multiple FGFRs is desirable to achieve tumor regression. Furthermore, we will show combination studies with relevant standard of care therapies in models of lung and renal cancer.

Taken together, our preclinical data strongly supports the clinical evaluation of MM-161 in cancer patients.

Citation Format: Tamara Dake, Greg Finn, Melissa Geddie, Neeraj Kohli, Maja Razlog, Lihui Xu, Violette Paragas, Haluk Yuzugullu, Sara Ghassemifar, Yasmin Hashambhoy-Ramsay, Charlotte McDonagh, Marco Muda, Birgit Schoeberl. MM-161, a first-in-class pan-FGFR antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 22. doi:10.1158/1538-7445.AM2017-22

Abstract 3842: Design and engineering of TRAIL fusion proteins for cancer therapy

Protein-based agonists of apoptotic death receptors have shown remarkable preclinical efficacy but limited clinical response. The short circulating half-life of recombinant human TRAIL and the necessity of Fc-mediated clustering for potentiating agonistic antibodies against DR4 and DR5 have been proposed to be major impediments to the clinical success of this class. To address these limitations we have created Fc-scTRAIL, a single fusion polypeptide consisting of an IgG1 Fc region followed by three successive TRAIL monomers connected by two fifteen-amino acid linkers. While Fc-scTRAIL showed potent activity in vitro, we observed a low TM (48 °C) and rapid inactivation in serum indicating protein instability. Subsequently, we applied a directed evolution approach using yeast surface display to identify mutations that would stabilize the TRAIL trimer. When individual mutations were transferred to the Fc-scTRAIL format, we observed a dramatic increase in the TM (66-70 °C) while the combination of three mutations improved serum stability by ten-fold. Stabilized Fc-scTRAIL shows greater pro-apoptotic activity across a panel of cancer cell lines when compared to mapatumumab (anti-DR4) and drozitumab (anti-DR5), or the combination of antibodies even in the presence of anti-Fc cross-linking. Moreover, anti-Fc did not improve Fc-scTRAIL activity suggesting that the hexavalent design of the molecule maximizes death receptor activation. Currently, in vivo evaluation of Fc-scTRAIL for pharmacokinetic properties and activity is underway. We believe this format, when combined with an appropriate patient selection strategy, will result in improved clinical outcomes.

Citation Format: Eric M. Tam, Hannah Hudson, Tamara Dake, Sara Ghassemifar, Andreas Raue, Yasmin Hashambhoy-Ramsay, Stephen L. Sazinsky, Anahita Daruwalla, Neeraj Kohli, Lihui Xu, Charlotte F. Mc Donagh, Birgit Schoeberl, Diana H. Chai. Design and engineering of TRAIL fusion proteins for cancer therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3842.

Mutations in Lyar and p53 are synergistically lethal in female mice

BACKGROUND

Ly-1 antibody reactive clone (LYAR) is a nucleolar zinc finger protein that has been implicated in cell growth, self-renewal of embryonic stem cells, and medulloblastoma. To test whether LYAR is critical for cell growth and development, we generated Lyar mutant mice.

METHODS

Mice carrying the mutant Lyar(gt) allele were generated from embryonic stem cells that contained a gene-trap insertion in the Lyar gene. Phenotypic analyses were performed on Lyar mutant mice and mouse embryonic fibroblasts. Lyar(gt/gt) mice were crossed to mice lacking the p53 tumor suppressor protein and Lyar/p53 compound mutants scored for external abnormalities.

RESULTS

Lyar(gt/gt) homozygotes are viable, fertile, and indistinguishable from wild type littermates. However, the growth of Lyar(+/gt) and Lyar(gt/gt) mouse embryonic fibroblasts (MEFs) was impaired, coincident with an increase in the steady-state level of p53 and a key p53 effector of growth arrest, p21, suggesting that a cellular stress response is triggered in the absence of a wild type level of LYAR. Remarkably, the majority of Lyar(+/gt) and Lyar(gt/gt) female mice lacking p53 mice failed to survive. The neural tube defect (NTD) exencephaly was observed in ≈26% and ≈61% of female Lyar(+/gt;) p53(-/-) and Lyar(gt/gt;) p53(-/-) embryos, respectively.

CONCLUSIONS

Lyar/p53 mutant mice represent a new digenic model of NTDs. Furthermore, these studies identify Lyar as a novel candidate gene for a role in human NTDs. These results provide new data to support the idea that loss of a p53-mediated developmental checkpoint may increase the risk of NTDs owing to some germline mutations.

MDM2 antagonism by nutlin-3 induces death in human medulloblastoma cells

A critical component of the cellular stress response, the p53 tumor suppressor protein must be functional for many cancer therapies to be effective. Adjuvant therapies that augment p53 function are predicted to sensitize tumor cells to cancer therapies that rely upon p53 for their efficacy. Of those strategies currently being explored to enhance p53 function, inhibition of the ubiquitin ligase, MDM2, a negative regulator of p53, has shown promise. Here, we investigated whether MDM2 antagonism might be effective in inducing cell death in human medulloblastoma (MB) cells. Nutlin-3, a small-molecule inhibitor of MDM2, potently induced apoptosis in MB cells with wild-type TP53. Moreover, nutlin-3 potentiated p53 activation and growth impairment of MB cells in combination with the classic DNA-damaging agent doxorubicin. Together, these results support the concept that MDM2 antagonists may be therapeutically beneficial for patients with MB tumors.

p53 in the CNS: Perspectives on Development, Stem Cells, and Cancer

The p53 tumor suppressor potently limits the growth of immature and mature neurons under conditions of cellular stress. Although loss of p53 function contributes to the pathogenesis of central nervous system (CNS) tumors, excessive p53 function is implicated in neural tube defects, embryonic lethality, and neuronal degeneration. Thus, p53 function must be tightly controlled. The anti-proliferative properties of p53 are mediated, in part, through the induction of apoptosis, cell cycle arrest, and senescence. Although there is still much to be learned about the role of p53 in these processes, recent evidence supports exciting new roles for p53 in a wide range of processes, including neural precursor cell self-renewal, differentiation, and cell fate decisions. Understanding the full repertoire of p53 function in CNS development and tumorigenesis may provide us with novel points of therapeutic intervention for human diseases of the CNS.