Targeted therapeutics platform
Selvita’s targeted therapeutics platform can be broadly divided into two types of projects: kinase inhibitors and synthetic lethality projects. The kinase inhibitor platform includes:
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Clinical-stage SEL24 in Phase I for relapsed/refractory AML is out-licensed to Menarini.
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Second lead project, SEL120, partnered with the Leukemia & Lymphoma Society, is undergoing regulatory toxicity studies and the Phase I could start in H119.
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Established in September 2013, the collaboration with H3 Biomedicine (Eisai) involves novel small molecule compounds for new kinase targets associated with cancer development.
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The collaboration with Felicitex Therapeutics was established in November 2014. It focuses on the phenomenon of cancer quiescence, a novel approach with expected efficacy against quiescent cancer cells that are not actively proliferating and are therefore less susceptible to classical chemotherapy drugs.
The other strategic area of focus in this platform is synthetic lethality. One of the disclosed targets is BRM/SMARCA2. A preclinical candidate BRM/SMARCA2 inhibitor is expected to be identified in 2020.
SEL24 – Phase I/II trial readout in 2019
The most advanced asset, SEL24, or MEN1703 under Menarini, a dual inhibitor of PIM and FLT3 kinases, is undergoing a Phase I/II trial in relapsed/refractory AML patients, with results expected in 2019. The asset was out-licensed in March 2017 to Berlin-Chemie (part of the Menarini Group) for an upfront payment of €4.8m, a total of €89.1m in potential milestone payments, and non-specified single- to low double-digit royalties and cost sharing. Initially, Selvita continued to manage the Phase I/II trial, but the handover process was completed in June 2018, and the company’s resources and capacity can therefore now be dedicated to other projects in the pipeline. The Phase I/II study is an open-label, dose-escalation study. Part 1 of the trial aimed to establish the recommended dose, which is being evaluated in Part 2 for safety, but also for initial efficacy in several cohorts.
SEL24: Unique mechanism of action
SEL24 specifically inhibits PIM- and FLT3-related pathways and exhibits broader anti-tumour activity in AML compared to selective FLT3-ITD or PIM inhibitors. FMS-like tyrosine kinase receptor-3 gene internal tandem duplication (FLT3-ITD mutation) is one of the most common genetic lesions in AML (around 25% of newly diagnosed AML cases) and, although its inhibition has been shown to be effective in clinical trials, resistance to treatment develops rapidly. PIM kinases are major oncogenes and downstream targets with expression triggered by FLT3-induced STAT5 activity. The expression of PIM kinases amplifies FLT3’s oncogenic potential in addition to other pro-oncogenic signalling, thus presenting a rationale for a dual FLT3/PIM inhibition. Previously, third-party data have shown PIM expression increases cancer resistance to FLT3-ITD inhibitors, while PIM inhibition would restore cancer sensitivity to FLT3 inhibitors. Selvita’s SEL24, a first-in-class dual inhibitor of PIM and FLT3 kinases, can simultaneously inhibit both kinases and provides a novel treatment strategy.
The rationale of SEL24 mechanism of action has been tested by Selvita in various in vitro and in vivo studies comparing it to control or active treatment with standalone PIM (AZD1208, AstraZeneca) or FLT3-ITD (AC220/quizartinib, Daiichi Sankyo) inhibitors and recently published in an article in Oncotarget:
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Synergistic effect of dual inhibition. SEL24 has been described as a potent, dual inhibitor of PIM and FLT3 kinases and has anti-proliferative activity in AML cell lines, which was broader than that of selective PIM inhibitors or FLT3 inhibitors. The combination of AZD1208 and quizartinib also demonstrated a synergistic effect further supporting a dual specificity treatment rationale.
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Efficacy in vivo animal models (Exhibit 2). SEL24 was tested in several in vivo xenograft models.
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In a single-agent test in mice bearing FLT3-ITD tumours (MV-4-11) a dose dependent reduction in tumour volume by 67-82% has been observed (Exhibit 2A). In the FLT3-WT (wild-type, ie not mutated) model (MOML-16) c 100% tumour growth inhibition was observed at certain doses.
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To compare the efficacy of SEL24 versus PIM inhibitor AZD1208 and FLT3-ITD inhibitor AC220, the drugs were used in two models – MOLM-13 (FLT3-ITD) and KG-1 (FLT3-WT). SEL24 reduced tumour growth by c 50% in both models. AZD1208 had a variable effect with 20% response in FLT3-ITD and 60% in FLT3-WT. AC220 had no effect in FLT3-WT mice, but reduced the volume growth in the FLT3-ITD tumour by 100% surpassing the effect of SEL24 (Exhibits 2B, A). Researchers stipulated that this could have been caused by SEL24’s relatively short half-life in mice. Previously, other in-house data (not included in the article) showed higher tumour growth inhibition by SEL24 with twice-daily dosing (the current study used a once-daily regime) (Exhibit 2B).
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Of particular note is that SEL24 had a largely similar effect in both the FLT3-WT and FLT3-ITD models (although in the FLT3-ITD model there is the potential to observe even higher efficacy with different dose regimens as explained above). PIM kinases are known to be expressed also in FLT3-WT AML cells. Therefore SEL24 could, theoretically, potentially be used to treat AML patients even with FLT3-WT status.
Exhibit 2: In vivo models with SEL24, AZD1208 (PIM inhibitor) and AC220 (FLT3 inhibitor)
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Source: W Czardybon et al. MOLM-16, MV-4-11, KG-1 and MOLM-13 cell lines were implanted subcutaneously in immunodeficient mice.
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AML still an unmet need; changing treatment paradigm
AML normally originates in the bone marrow (where new blood cells are made), but often quickly moves into the blood, resulting in uncontrolled growth and accumulation of malignant white blood cells, which fail to function normally and interfere with the production of normal blood cells. AML is the most common type of acute leukaemia in adults and affects nearly 40,000 patients in the EU and US (new cases per year). The five-year survival rate for all AML patients, irrespective of age or genetic status, is around 23%. The standard-of-care treatment for AML has not changed significantly for many decades, primarily based on chemotherapy (cytarabine with anthracycline or mitoxantrone) and followed by a stem cell transplant where appropriate. The goal of treatment is to reduce the blasts in the bone marrow to below 5% and return the blood cell counts to normal levels. A bone marrow transplant is generally recognised as the only curative treatment option, but is not always appropriate.
Rydapt (midostaurin, Novartis) was the first approved drug that specifically targets FLT3 for the treatment of adults with newly diagnosed FLT3-ITD AML in combination with standard of care chemotherapy. This was the first large Phase III RATIFY trial to confirm a therapeutic benefit of FLT-ITD inhibition in AML patients. Overall survival was increased from approximately two years to just over six years and there was a 23% reduction in risk of death compared to the placebo arm (hazard ratio 0.77, p=0.0074). The FDA granted breakthrough therapy designation and a priority review into midostaurin’s NDA application and ultimately approved in April 2017. Consensus sales forecast Rydapt sales of $374m in 2024 (EvaluatePharma).
On 28 November 2018, the FDA approved gilteritinib (Xospata, Astellas) as monotherapy for adults with FLT3-positive AML in a relapsed or refractory setting. Approval was based on results of the Phase III ADMIRAL trial. Treatment with gilteritinib resulted in complete remissions (CRs), or CRs with partial haematologic recovery in 21% of patients (95% CI 14.5%–28.8%). Consensus forecast Xospata sales of $451m in 2024.
The latest significant achievement in the FLT3 inhibitor development area was Daiichi Sankyo’s results presentation from its Phase III QuANTUM-R study at the European Hematology Association (EHA), on 14-17 June in Stockholm, Sweden. The trial tested quizartinib as a salvage therapy in patients with relapsed/refractory AML with FLT3-ITD mutations after first-line treatment with or without haematopoietic stem cell transplantation. The results demonstrated that quizartinib significantly prolonged overall survival (OS) compared to standard-of-care salvage chemotherapy (27% versus 20% respectively, at week 52). The FDA granted priority review to quizartinib. Consensus sales forecast Rydapt sales of $374m in 2024 (still in the rapid growth phase).
Outside the FLT3 inhibitor space, the FDA approved two other novel drugs – glasdegib (Daurismo, Pfizer) in November 2018 and venetoclax (Venclexta, AbbVie/Roche). Daurismo, a hedgehog pathway inhibitor, was approved for use in combination with low-dose cytarabine for newly diagnosed, frail AML patients (aged 75 years or older and ineligible for intensive chemotherapy). Venclexta, a BCL-2 inhibitor, was approved for a similar group of newly-diagnosed, frail AML patients in combination with azacitidine or decitabine or low-dose cytarabine. Venclexta has received breakthrough designation from the FDA. While both novel drugs add to treatment options for AML, they target a specific group of patients, who are ineligible for more aggressive therapies. Even with this restriction, the consensus sales estimates for Daurismo are at $413m and at $812m for Venclexta in AML by 2024.
SEL120
SEL120 is a first-in-class selective CDK8 inhibitor. Depending on subtypes, cyclin-dependent kinases (CDKs) play varied roles in the control of cell cycle, proliferation and mRNA transcription. Specifically, CDK8 is uniquely differentiated and is a part of a multi-protein complex that regulates gene expression. So far, preclinical studies point to potential efficacy in haematological malignancies, which should be further explored in Phase I. Preclinical efficacy has also been established in solid tumours, such as colorectal cancer or triple-negative breast cancer, and in combination therapies with immunooncology products, which are all potential indications for expansion in later trials. Preparations for the clinical development of SEL120 are ongoing and Selvita plans to file an IND application in Q119, with a Phase I trial following subsequently.
SEL120 development supported by Leukemia & Lymphoma Society
In August 2017, Selvita announced a partnership agreement with the Leukemia & Lymphoma Society (LLS) to co-fund further preclinical development of SEL120 for AML patients. The rationale for this indication is that SEL120’s unique mechanism of action does not overlap with existing therapies and may allow the development of synergistic combination treatments. According to the deal terms, LLS will provide up to $3.25m in funding over the next four years. This should allow SEL120 to progress though IND-enabling studies through to Phase I in AML. Founded in 1949, LLS is headquartered in the US and has invested over $1bn in various projects so far.
CDK8 inhibitor mechanism of action
This year Selvita presented new preclinical data at multiple conferences, while previous data have been discussed in our past outlook reports. The results of Selvita’s collaboration with Lund University were presented during the annual American Society of Hematology (ASH) meeting in December 2018, one of the highest-profile research conferences in haematology-oncology. The presentation included in vivo results from murine AML model and human patient-derived xenograft (PDX) AML model. In the first instant, the treatment of leukemic mice with SEL120 resulted in reduced leukemia burden in bone marrow and blood. In the PDX model SEL120 completely eliminated circulating primitive CD45+/CD34+ leukemic cells in comparison to control animals (Exhibit 3A). Fewer CD34+ cells were observed in bone marrow in SEL120 treated group than control (Exhibit 3B) and spleen weight was also significantly lower in SEL120 group (spleen is enlarged in AML) (Exhibit 3C). These in vivo results demonstrate strong anti-leukaemic activity.
Exhibit 3: SEL120 demonstrated an anti-leukaemic effect in an AML PDX mouse model
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New preclinical data was also presented at the EORTC-NCI-AACR Molecular Targets and Cancer Therapeutics Symposium, 13–16 November 2018, Dublin, Ireland. The presentation included an overview of the recent preclinical data accumulated with SEL120 in both AML and acute lymphoblastic leukaemia (ALL) as a standalone therapy or in combinations. Some of the highlights include:
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SEL120 was effective with nanomolar activity in cell lines with activated STAT signalling and CD34 expression, which are features of leukaemia stem cells (LSCs). LSCs contribute to AML relapse through treatment-resistant clones. SEL120 induced cell differentiation, ie immature leukaemic cells turn into normal mature blood cells (tested in LSC-like TEX cell line).
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In an in vivo of model where immunodeficient mice were injected subcutaneously with AML cell lines, a significant synergistic therapeutic effect has been observed in animals that received both SEL120 and venetoclax (ABT-119) (Exhibit 4). As described in the section entitled AML still an unmet need; changing treatment paradigm above, venetoclax is now approved as frontline therapy for frail, elderly AML patients.
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In vitro results also demonstrated SEL120 is active in acute T-cell lymphoblastic leukaemia. For example, in DND-41 cell line SEL120 demonstrated sub-micromolar activity. These cells have activating Notch pathway mutation, which are present in around 60% of human T-cell ALL cases.
Exhibit 4: SEL120 is active in combination therapy with recently approved for AML venetoclax (ABT-199)
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Source: Selvita; M. Mazan et al, presentation at the EORTC-NCI-AACR, November 2018. Note: cell line-derived mouse model (BALB/c Nude + MV4-11)
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Selvita will continue testing SEL120 in preclinical proof of concept in vivo models to better inform clinical efficacy trials with humans. In plans are tests whether SEL120 treatment extends survival of mice with AML in syngeneic and patient-derived xenograft models. One of the more notable news in the CDK8 inhibitor area was Merck & Co licensing agreement for a selective CDK8/CDK19 inhibitor from Harvard University in March 2016. The deal included an upfront payment of $20m and tiered royalties, which was the largest licence fee for technology developed at the university. The agreement involved compounds derived from a natural compound, cortistatin A, and recently published articles showing anti-leukaemic in vitro and in vivo efficacy, which adds to Selvita’s preclinical data.