2021 ASH: Combining the IAP Antagonist Tolinapant with a DNA Hypomethylating Agent Enhances Immunogenic Cell Death in Preclinical Models of T-Cell Lymphoma

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Combining the IAP Antagonist Tolinapant with a DNA Hypomethylating Agent Enhances Immunogenic Cell Death in Preclinical Models of T-Cell Lymphoma

Abstract:

Introduction:  Tolinapant is a potent, non-peptidomimetic antagonist of cIAP1, cIAP2 and XIAP.  In ongoing Phase 2 trial (NCT02503423), tolinapant has shown activity against highly pre-treated peripheral and cutaneous T-cell lymphoma (Samaniego et al., Hematological Oncology, 2019). Hypomethylating agents (HMAs) have also shown clinical responses in some subsets of PTCL (Lemonnier et al., Blood, 2019). Both HMAs and IAP antagonists show immunomodulatory anti-cancer potential in pre-clinical studies. A Phase 1 clinical study investigating the combination of tolinapant and ASTX727 (oral decitabine) in AML is currently in progress (NCT04155580). Here we have undertaken a biomarker-driven approach to understand the potential for induction of immunogenic forms of cell death (ICD), such as necroptosis, by rational combination of our clinical compounds in pre-clinical models of T-cell lymphoma (TCL).

Methods:  On-target effects of decitabine and tolinapant were measured by analysing levels of DNMT1 and cIAP1, respectively, by Western blotting in mouse and human cell lines. Levels of key apoptosis, necroptosis or pyroptosis biomarkers were also monitored by Western blotting to provide evidence of lytic cell death contributing to a potential immune response. RIPK3- or MLKL-knockout cell lines were generated by CRISPR to demonstrate involvement of necroptosis in drug-induced cell death in a T-cell lymphoma cell line (BW5147.G.1.4) in vitro. Cell death was monitored by viability (CellTiterGlo) or real-time microscopy (IncuCyte) assays. Levels of key inflammatory mediators or DAMPS were measured in tissue culture supernatants and mouse plasma by Luminex assay (Ampersand).

Results:  Combined treatment of tolinapant and decitabine led to depletion of cIAP1 and DNMT1 in TCL cell lines, demonstrating on-target activity of tolinapant and decitabine, respectively. The combination of tolinapant and decitabine acted synergistically in mouse and human T-cell lymphoma cell lines to reduce viability in proliferation assays.

Necroptosis was induced by decitabine or tolinapant alone in mouse TCL cell lines with robust activation of the RIPK1/RIPK3/MLKL necroptosis pathway when caspase activity was inhibited, and the combination of both agents enhanced loss of viability.

Furthermore, we demonstrated decitabine treatment led to re-expression of both RIPK3 and MLKL in mouse cell lines, supporting published evidence that methylation can silence these key biomarkers (Koo et al., Cell Research, 2015; Koch et al., Neoplasia, 2021). Enhanced release of chemokine, cytokine and DAMPs was demonstrated with the combination of agents in vitro and in vivo.

By removal of key necroptosis pathway components using CRISPR, we confirmed the importance of this lytic cell death pathway by demonstrating that RIPK3-/- and MLKL-/- T-cell lymphoma (BW5147.G.1.4) cell lines had reduced necroptosis potential after treatment with tolinapant or decitabine alone or in combination; and demonstrate reduced release of inflammatory mediators in vitro.

Finally, our in vivo evaluation of the combination of agents in mouse syngeneic models suggested that increased anti-tumour activity and immune-potentiating systemic biomarker modulation can be achieved with a tolerated dosing regimen of both compounds.

Conclusion:  These data demonstrate that decitabine enhances immunogenic cell death induced by tolinapant through the re-expression of genes in the necroptotic pathway.  This finding provides strong rationale to explore this combination clinically.

2021 ASH: Results from a Global Randomized Phase 3 Study of Guadecitabine (G) Vs Treatment Choice (TC) in 302 Patients with Relapsed or Refractory (r/r) Acute Myeloid Leukemia after Intensive Chemotherapy (ASTRAL-2 Study)

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Results from a Global Randomized Phase 3 Study of Guadecitabine (G) Vs Treatment Choice (TC) in 302 Patients with Relapsed or Refractory (r/r) Acute Myeloid Leukemia after Intensive Chemotherapy (ASTRAL-2 Study)

Abstract:

Background: Guadecitabine (G) is a next generation subcutaneous (SC) hypomethylating agent (HMA) resistant to degradation by cytidine deaminase which results in prolonged in vivo exposure to the active metabolite decitabine. We conducted a large global randomized phase 3 study (ASTRAL-2) of G vs TC in AML patients who were either refractory to or relapsed (r/r) after prior anthracycline-based intensive chemotherapy with or without hematopoietic cell transplant (HCT).

Methods:  r/r AML patients were randomized to G (60 mg/m2 SC/d for 10 days in first 1-2 cycles followed by 5-day cycles Q 28 days) vs Treatment Choice (TC). TC were preselected prior to randomization to either low intensity (LI) treatment; high intensity (HI) chemotherapy; or Best Supportive Care (BSC).  LI choices were other HMAs of azacitidine or decitabine, or low-dose Ara-C (LDAC) at their standard doses. HI choices were high-dose Ara-C (HiDAC), MEC, or FLAG± Ida combination chemotherapy at standard doses. Primary endpoint was overall survival (OS) based on ITT analysis with secondary endpoints including 12 and 24-month survival rates, complete response (CR), event-free survival (EFS), and safety. P values for secondary endpoints and subgroups are nominal as there was no adjustment of p values for multiple analyses.

Results: 302 patients were randomized to G (148) or TC (154). Preselected TCs were mainly LI (77%) predominantly HMAs (86% of the patients randomized to LI), or HI (21%), with only 6 patients (2%) in the BSC subset. Baseline variables were well balanced across the 2 treatment arms. For G vs TC respectively, age ≥65 y in 51.4% vs 40.3% with median age 65y vs 63y, ECOG PS 2 in 15.5% vs 20.8%, poor risk cytogenetics in 44.6% vs 42.2%, refractory AML in 44.6% vs 33.1%, prior HCT in 18.2% vs 26%, a majority of patients were in second or subsequent relapse after ≥ 2 prior therapies (54.7% vs 56.5%).

Median number of treatment cycles was short (3 cycles for G vs 2 cycles for TC). Median follow up was 21.6 months.  Most common causes of treatment discontinuation were disease progression (35.2% for G vs 38.1% for TC), or death (15.2% for G vs 18.4% for TC).

Median OS on G was 6.4 months vs 5.4 months for TC and not statistically significant (OS HR 0.88, 95% CI 0.67, 1.14, log rank p value 0.3). There was no significant difference in OS between G and each of the LI and HI preselected subsets. However, several other planned prospective subgroups favored G with OS HR 95% CI upper limit ≤ 1.0 including patients <65y (HR 95% CI 0.47, 0.97, p 0.032) ; ECOG PS 0-1 (HR 95% CI 0.57, 1.0, p 0.049); refractory AML (HR 95% CI 0.38, 0.89, p 0.013); lower peripheral blood (PB) disease burden of ≤ 30% PB blasts (HR 95% CI 0.46, 0.92, p 0.015); and those who received at least 4 cycles in either treatment arm (HR 95% CI 0.36, 0.95, p 0.031).  The 12- and 24-month survival rates for G vs TC respectively were 32% vs 26%; and 19% vs 10%.  Median EFS was short with 3 months for G vs 2.4 months for TC; log rank p 0.005. CR rate was 12.8% for G vs 7.1% for TC (p 0.051). CR + CR with partial hematologic recovery (CRh) rate was double for G with 16.9% compared to 7.8% for TC (p 0.007). Composite CR (CRc) or CR+ CR with incomplete hematologic recovery (CRi) rate was 27% for G vs 14.3% for TC (p 0.003).

Adverse events (AEs) of grade ≥3, regardless of relationship to treatment, were 89% on G vs 84% on TC. Most common Grade ≥3 AEs for G vs TC respectively were febrile neutropenia (38.6% vs 38.1%); neutropenia (32.4% vs 17%); thrombocytopenia (28.3% vs 29.9%); anemia (21.4% vs 24.5%); pneumonia (18.6% vs 20.4%); and sepsis (11.7 vs 10.9%).  None of the differences were significant except for neutropenia (p 0.003).

Summary/Conclusions: In this randomized study in r/r AML after intensive chemotherapy, G did not significantly improve OS compared to standard of care TC composed mainly of LI treatment with other HMAs. The data suggest that G may be better than TC in in some of the secondary endpoints (24-month survival rate, EFS, CR, CR+CRh, and CRc). Prospective subgroup analyses of OS suggest that younger (<65 y), more fit patients (PS 0-1); with lower PB disease burden (PB blasts ≤ 30%), and those who could receive at least 4 cycles may benefit from G. The results of secondary endpoints and subgroup analyses should be interpreted with caution. Grade ≥3 AEs were the expected hematological and infection AEs with no significant differences between G and TC except for significantly higher incidence of neutropenia with G.

2021 ASH: Oral decitabine/cedazuridine in Patients with Lower Risk Myelodysplastic Syndrome: a Longer-Term Follow-Up of from the ASCERTAIN Study

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Oral decitabine/cedazuridine in Patients with Lower Risk Myelodysplastic Syndrome: a Longer-Term Follow-Up of from the ASCERTAIN Study

Abstract:
Background/Introduction: Lower-risk (IPSS low risk and Int-1) myelodysplastic syndromes (MDS) are typically treated supportively to address cytopenias. DNA methyltransferase inhibitors (DNMTi) such as azacitidine and decitabine (DEC) are FDA-approved for higher risk MDS patients (pts), and while the DEC USPI includes IPSS Int-1 pts, it is not widely used in this population. Approved intravenous (IV) or subcutaneous (SC) regimens require 5-7 days of treatment every month burdening older cancer pts due to daily travel and treatment time and may increase potential risk from pandemic SARS-CoV-2 infection. Because DNMTis are rapidly degraded by cytidine deaminase (CDA) in the gut and liver, oral availability has only been recently possible. A randomized study with CC-486, an oral formulation of azacitidine, in the Int-1 population showed a median overall survival (mOS) of approximately 17 months for both placebo and treated patients (Garcia-Manero, 2021). Oral DEC 35 mg/cedazuridine 100 mg (ASTX727) or DEC-C, is an oral fixed dose combination (FDC) of DEC and the CDA inhibitor cedazuridine (CED) resulting in equivalent exposure (99%; 90% CI 93% to 106%) to standard IV DEC 20 mg/m2 for 5 days in an intra-patient randomized cross-over study (Garcia-Manero et al, ASH 2019). Here, we present data on patients with lower risk MDS from that study.
Methods: We used a randomized cross over design with pts randomized 1:1 in the first 2 cycles to either Sequence A: (DEC 35 mg/ CED 100 mg in Cycle 1 and IV DEC at 20 mg/m2 in Cycle 2), or Sequence B (IV DEC in Cycle 1 and oral DEC/CED in Cycle 2). Cycles were repeated every 28 days unless delays were needed, and all patients received oral DEC-C in Cycles 3+ until disease progression or unacceptable toxicity. We conducted an intra-patient comparison of DEC PK (DEC AUC equivalence over 5 days of dosing). Pts were eligible as per the FDA-approved label of IV DEC (MDS pts by FAB classification including CMML, or MDS IPSS Intermediate-1, 2 or high-risk pts). Clinical endpoints were best response as assessed by an independent expert panel according to IWG 2006 response criteria, transfusion independence (TI), overall survival (OS), and safety.
Results: Of the 133 pts treated in ASCERTAIN, 69 had a diagnosis of lower-risk MDS (93% Int-1, 7% LR). Median age was 70.0 years (range 45-87), 65% were male, median weight was 84 kg (range 50-127), median baseline hematologic parameters were: hemoglobin 89 g/L (range 69.8-146.5), WBCs 1.50 X 109/L (range 0.11-7.1), platelets (plt) 86 x 109/L (range 5-703), bone marrow blasts 4% (range 0-18), cytogenetics: 7 (10.1%) poor-risk, 21 (30.4%) intermediate risk, 37 (53.6%) better-risk, 4 (5.7%) missing or not evaluable. 27(39%) of the pts were RBC transfusion dependent (TD) and 6 (9%) plt TD. 17 (25%) had received prior MDS treatment, 3% prior DNMTi. Pts received a median of 9 cycles of therapy (range 1-28). Treatment-emergent adverse events of CTCAE Gr 3 or higher in >10% of pts, independent of relationship to ASTX727, included cytopenias (neutropenia [59%], thrombocytopenia [58%], anemia [48%], leukopenia [26%]), febrile neutropenia (32%), and pneumonia (19%). Sixteen pts (23%) achieved Complete Response (CR), 18 (26%) had marrow CR (mCR), including 9 (13%) with hematologic improvement (HI). Overall Response rate (ORR; CR + PR+ mCR + HI) was 57%. Of those RBC or plt TD at baseline, 13 (48%) became RBC TI and 4 (67%) became plt TI. With approximately 32 months of median follow up, neither median leukemia-free survival (mLFS) nor mOS had been reached (Figure 1). Twelve pts (17%) went on to allogeneic stem cell transplant.
Conclusions: Oral decitabine/cedazuridine given as a FDC in MDS pts produced equivalent PK exposure to 20 mg/m2 IV DEC; in lower risk MDS pts with treatment indicated, the agent was generally well-tolerated with prolonged treatment and could result in mLFS and mOS which exceeds 32 months. This FDC and other dosing regimens of oral DEC-C should be further studied in this patient population.
References:
Garcia-Manero, et al, ASH 2019
Savona, et al, Int. MDS Symp. 2021
Garcia-Manero, et al,. J. Clin. Onc. 2021 39:13, 1426-1436

ASH 2021: A Phase 1 Study Evaluating ASTX727 (decitabine and cedazuridine) and Venetoclax in Combination Therapy in Newly Diagnosed AML Patients Unfit for Intensive Induction Chemotherapy

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A Phase 1 Study Evaluating ASTX727 (decitabine and cedazuridine) and Venetoclax in Combination Therapy in Newly Diagnosed AML Patients Unfit for Intensive Induction Chemotherapy

Abstract:

Introduction: The combination of a DNA methyltransferase inhibitor (DNMTi; parenteral azacitidine or decitabine) with the BCL2 inhibitor venetoclax is a newly established standard-of-care regimen for patients with newly diagnosed acute myeloid leukemia (AML) ineligible to receive intensive induction chemotherapy (DiNardo et al, 2020). Replacing the parenteral DNMTi with an oral DNMTi with equivalent exposure may provide the benefit of reducing patient and caregiver burden of chronic parenteral therapy, and may help responding patients stay on treatment longer. ASTX727 (a fixed-dose combination of decitabine 35 mg and cedazuridine 100 mg) is an oral DNMTi that provides equivalent exposure to its parenteral DNMTi at standard dosing (Savona et al, 2020) and is under evaluation in combination with venetoclax as an all-oral regimen.

Methods: This is an ongoing Phase 1 study being conducted at 7 US medical centers (ClinicalTrials.gov NCT04657081). Newly diagnosed AML patients 75 years or older, or with comorbidities that preclude use of intensive induction chemotherapy are eligible. The primary objective is to evaluate the effect of ASTX727 on the PK of venetoclax. Key secondary objectives are to evaluate the effect of venetoclax on the PK of ASTX727, and to determine the safety and efficacy profile for the combination. For Cycle 2 and beyond, ASTX727 is administered orally daily on days 1-5 and venetoclax 400 mg is administered orally daily on days 1-28 of 28-day cycles. For Cycle 1, ASTX727 is given in the same dose schedule while venetoclax is given as a ramp-up on days 1 and 2 according to the venetoclax US prescribing information (USPI); therefore, the PK studies are conducted during Cycle 2. Delay of subsequent cycles and venetoclax dose modifications for hematologic toxicities and anti-fungal concomitant medications follow the venetoclax USPI. Response assessments are evaluated using the 2017 ELN criteria (Döhner et al, 2017) and the CRh criterion (complete response [CR] with partial hematologic recovery) defined as those patients achieving marrow CR criteria but not peripheral blood count criteria and demonstrating an absolute neutrophil count >500/μL and platelet >50,000/μL (Kantarjian et al, 2017).

Results: At the data cut-off date of August 1, 2021, 15 AML patients have enrolled and received study treatment. Median age is 78 years (range 66 – 84) and 9 (60%) are males. Of the 12 patients with data, 2 (17%), 6 (50%), and 4 (33%) patients are in the favorable, intermediate, and adverse risk ELN categories, respectively. Of the 15 dosed patients, 6 (40%) are diagnosed with AML with myelodysplasia-related changes. The median duration of exposure is 2 cycles (range 1-5) and 1.7 months (range 0.8-5.6). The most common adverse events (AEs) of Grade 2 or higher occurring in ≥10% of patients include neutropenia (5, 33%), febrile neutropenia (2, 13%), anemia (2, 13%), thrombocytopenia (2, 13%), vomiting (2, 13%), pneumonia (2, 13%), peripheral edema (2, 13%), hypertension (2, 13%) and vascular access complication (2, 13%). There are 17 serious AEs experienced in 7 patients; a grade 3 pneumonia and a grade 3 dysphagia are the only serious AEs assessed as related to ASTX727 and/or venetoclax and both events occurred in the same patient. Both AEs were part of the patient’s medical history. Two deaths have occurred to date: one patient due to rapidly progressive disease during Cycle 2 and one patient who achieved a best response of CRh transitioned to hospice due to progressive multiple myeloma. Of 9 patients with response assessments and evaluable data, 3 (33%) achieved CR and 4 (44%) achieved CRh as the best response for a composite CR+CRh rate of 78%. Preliminary PK data available from 9 patients show venetoclax exposures are not affected by coadministration of ASTX727and are similar to historical data. Exposures of decitabine and cedazuridine are consistent with the range seen in previous studies. Updated PK, safety, and efficacy data will be provided in December 2021.

Conclusions: A preliminary analysis of ASTX727 and venetoclax combination therapy in patients with newly diagnosed AML unfit for intensive induction chemotherapy demonstrate expected PK data, and a similar safety and efficacy profile to the approved combination therapy of a DNMTi and venetoclax. These preliminary data suggest that an all-oral regimen of a DNMTi in combination with venetoclax is feasible and should be investigated further.

Ferrari, et al. “Antagonism of inhibitors of apoptosis proteins reveals a novel, immune response-based therapeutic approach for T-cell lymphoma”, 2021

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Blood Advances. 2021 Oct 26;5(20):4003-4016.

DOI: 10.1182/bloodadvances.2020003955

2021 Virtual 16th MDS Conference: Prolonged survival observed in 133 MDS patients treated with oral decitabine/cedazuridine

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Prolonged survival observed in 133 MDS patients treated with oral decitabine/cedazuridine

Abstract: 

Background and aims

DNMTi are active in MDS treatment, however chronic parenteral therapy constitutes a burden for these patients, often elderly with co-morbid conditions. Oral decitabine(35 mg)/cedazuridine(100mg) given Days 1-5 every 28 days produces equivalent pharmacokinetic exposure (AUV) to 20 mg/m2 IV decitabine dosing (Garcia-Manero, ASH 2019).

Methods

This randomized, cross-over study enrolled MDS/CMML subjects appropriate to receive IV decitabine per the US label. Subjects either received IV decitabine or oral decitabine/cedazuridine, followed by the converse in C2, allowing intrapatient PK comparison. All subjects received oral decitabine/cedazuridine for subsequent cycles providing longer term safety and efficacy data.

Results

133 patients (IPSS HR: 16%, Int-1: 48%, Int-2: 20%, LR:4%, CMML:12%) were enrolled (US and Canada). The median age was 71y; 65% Male; 41% RBC and 9% platelet transfusion dependent, respectively. Subjects received a median of 9 cycles of treatment and 26% proceeded to HCT, typically after 4-6 cycles. The most common adverse events of thrombocytopenia, neutropenia, and anemia were consistent with expected AEs with parenteral DNMTi. Complete Response(CR) was achieved in 22%(95% CI 15.1,29.8), and overall response (CR + Partial Response + marrow CR + Hematologic Improvement) of 62% (95% CI 52.8, 69.9) was similar to seen with parenteral DNMTi.  K-M estimated mOS was 31.7 months.

Conclusion

Oral decitabine/cedazuridine is the only DNMTi demonstrating equivalent pharmacokinetic exposure to its IV form, and led to expected equivalent responses, with mOS of 31.7mo in this study. Additional studies using oral decitabine/cedazuridine in combination with new oral agents for hematological disease are warranted.

2021 Blood Virtual Congress: Clinical Efficacy and Safety of Oral Decitabine/Cedazuridine in 133 Patients with Myelodysplastic Syndromes (MDS) and Chronic Myelomonocytic Leukemia (CMML)

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Clinical Efficacy and Safety of Oral Decitabine/Cedazuridine in 133 Patients with Myelodysplastic Syndromes (MDS) and Chronic Myelomonocytic Leukemia (CMML)

Abstract:

Aim: Confirm fixed dose combination (FDC) of oral decitabine/cedazuridine produces similar clinical activity vs. IV decitabine. Background: An oral FDC of 35 mg decitabine and 100 mg of CDA inhibitor cedazuridine has shown 99% (90% CI 93% to 106%) equivalent exposure to 20 mg/m2 IV decitabine in a randomized cross-over study(1). If oral decitabine/cedazuridine treatment produces similar clinical results its use may decrease the burden associated with chronic parenteral hypomethylating agent (HMA) therapy in MDS and CMML.

Methods: Randomized cross over design: 133 subjects treated in US or Canada.
Primary PK endpoint: decitabine AUC equivalence over 5 days of dosing. Efficacy endpoints: best response per IWG 2006, transfusion independence, OS, and safety. AEs were graded by CTCAE v 4.03.

Results:  Patient Characteristics: median age 71.0 years; 65% male; 88%MDS/12%CMML; 43% either RBC or platelet baseline transfusion-dependent; 25% poor-risk cytogenetics, and 42% baseline BM blasts >5%. Best Response: CR in 29/133 patients (22%), mCR with HI:17% (without HI 16%), and HI: 7.5%, for an overall objective response (CR+mCR+HI) of 62%; 26% proceeded to transplant. With median follow up of 24.7 months, median OS had not been reached. Treatment-Emergent AEs (Grade ≥3 regardless of causality): thrombocytopenia (61%), neutropenia (58%), anemia (51%), febrile neutropenia (32%), leukopenia (25%), and pneumonia (18%), of patients treated with oral decitabine/cedazuridine (excluding IV decitabine cycle).

Conclusion: Efficacy and safety from oral decitabine 35 mg/ cedazuridine 100 mg daily for 5 days every 28 days are consistent with historical clinical data from standard IV decitabine 20 mg/m2 daily for 5 days. Oral decitabine/cedazuridine is the only oral HMA with systemic exposure equivalent to its injectable drug. Further investigation of oral decitabine/cedazuridine in all-oral combination studies is warranted and underway.

References:  Garcia-Manero, et al, Blood 2019; 134 (Supplement_1): 846. doi: https://doi.org/10.1182/blood-2019-122980

Heightman et al., “Discovery of ASTX029, A Clinical Candidate Which Modulates the Phosphorylation and Catalytic Activity of ERK1/2”

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https://pubs.acs.org/doi/full/10.1021/acs.jmedchem.1c00905

Abstract

Aberrant activation of the mitogen-activated protein kinase pathway frequently drives tumor growth, and the ERK1/2 kinases are positioned at a key node in this pathway, making them important targets for therapeutic intervention. Recently, a number of ERK1/2 inhibitors have been advanced to investigational clinical trials in patients with activating mutations in B-Raf proto-oncogene or Ras. Here, we describe the discovery of the clinical candidate ASTX029 (15) through structure-guided optimization of our previously published isoindolinone lead (7). The medicinal chemistry campaign focused on addressing CYP3A4-mediated metabolism and maintaining favorable physicochemical properties. These efforts led to the identification of ASTX029, which showed the desired pharmacological profile combining ERK1/2 inhibition with suppression of phospho-ERK1/2 (pERK) levels, and in addition, it possesses suitable preclinical pharmacokinetic properties predictive of once daily dosing in humans. ASTX029 is currently in a phase I–II clinical trial in patients with advanced solid tumors.

Munck et al., “ASTX029, a Novel Dual-Mechanism ERK Inhibitor, Modulates Both the Phosphorylation and Catalytic Activity of ERK”

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https://mct.aacrjournals.org/content/early/2021/07/30/1535-7163.MCT-20-0909#:~:text=ASTX029%20is%20a%20highly%20potent,not%20directly%20inhibiting%20MEK%20activity

Abstract

The MAPK signaling pathway is commonly upregulated in human cancers. As the primary downstream effector of the MAPK pathway, ERK is an attractive therapeutic target for the treatment of MAPK-activated cancers and for overcoming resistance to upstream inhibition. ASTX029 is a highly potent and selective dual-mechanism ERK inhibitor, discovered using fragment-based drug design. Due to its distinctive ERK binding mode, ASTX029 inhibits both ERK catalytic activity and the phosphorylation of ERK itself by MEK, despite not directly inhibiting MEK activity. This dual-mechanism was demonstrated in cell-free systems, as well as cell lines and xenograft tumor tissue, where the phosphorylation of both ERK and its substrate, RSK, were modulated on treatment with ASTX029. Markers of sensitivity were highlighted in a large cell panel, where ASTX029 preferentially inhibited the proliferation of MAPK-activated cell lines, including those with BRAF or RAS mutations. In vivo, significant anti-tumor activity was observed in MAPK-activated tumor xenograft models following oral treatment. ASTX029 also demonstrated activity in both in vitro and in vivo models of acquired resistance to MAPK pathway inhibitors. Overall, these findings highlight the therapeutic potential of a dual-mechanism ERK inhibitor such as ASTX029 for the treatment of MAPK-activated cancers, including those which have acquired resistance to inhibitors of upstream components of the MAPK pathway. ASTX029 is currently being evaluated in a first in human Phase I-II clinical trial in patients with advanced solid tumors (NCT03520075).

2021 AACR: A first-in-human, Phase 1 study of ASTX029, a dual-mechanism inhibitor of ERK1/2, in relapsed/refractory solid tumors

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View Poster: A first-in-human, Phase 1 study of ASTX029, a dual-mechanism inhibitor of ERK1/2, in relapsed/refractory solid tumors Abstract: Background: The RAS-RAF-MEK-ERK pathway is commonly upregulated in human cancers. This is an open-label Phase 1 study of ASTX029, a dual-mechanism extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, in subjects with relapsed/refractory solid tumors (NCT03520075). Methods: The primary objectives are to identify a maximum tolerated dose and/or recommended Phase 2 dose. ASTX029 was administered orally daily of 21-day cycles as powder-in-bottle (PiB, Cohort 1/10mg) and tablet formulation (beginning with Cohort 6/80 mg) under fed conditions, and as tablet formulation under fasting conditions (beginning with Cohort 8/40 mg). Dose escalation occurred according to a “3+3 design” based on dose-limiting toxicity (DLT) events. Disease response was evaluated according to RECIST v1.1 and exploratory indicators, including tumor variant allele frequency changes detected by cell-free DNA (cfDNA) quantitation. Results: 56 subjects were treated with at least one dose of ASTX029 in Phase 1A (dose escalation). Of 46 subjects with data, 35 (76%) had any RAS mutations and 3 (9%) had BRAF mutations; 1 subject had both. At the 200 mg dose level (Cohort 5, PiB/fed), one of six evaluable subjects developed a DLT (grade 3 maculopapular rash). At the 280 mg dose level (Cohort 12, tablet/fasting), two subjects experienced grade 2 central serous retinopathy adverse events (CSR AEs) within a few days of dosing. These were the only CSR AEs noted and one event was declared a DLT. Both subjects recovered to baseline within days of dose interruption. One cohort level below this dose was expanded (Cohort 11/200 mg, tablet/fasting); this dose level was deemed safe (without a DLT or grade ≥2 visual AE in 7 subjects) and was selected for Phase 1B dose expansion. Mean pharmacokinetic (PK) exposure was 151% of target exposure, which is defined as the level expected to have biological activity based on animal studies. The most frequent grade ≥2 AEs assessed as drug-related included nausea (4 subjects, grade 2) and transaminitis (4 subjects: 3 grade 2, 1 grade 3). The grade 3 transaminitis occurred in a subject with metastatic sarcoma involving the liver. There was one serious AE of malaise considered related to study drug. Two subjects, one with KRAS-G12A and BRAF-D549N non-small cell lung cancer (120 mg) and one with KRAS-G12D metastatic pancreatic cancer (200 mg), achieved partial responses (cycle 15/ongoing and cycle 3/ongoing, respectively). In 2 subjects with stable disease as the best response, longitudinal cfDNA sequencing showed a decrease of tumor variant allele frequencies after 2 cycles of ASTX029, followed by a return to baseline levels before disease progression. The most common reason for ASTX029 discontinuation was disease progression. Conclusions: This Phase 1A study of the ERK1/2 inhibitor ASTX029 has identified a dose level of 200 mg daily of a 21-day cycle for investigation in the Phase 1B portion of the study. Pharmacokinetic and pharmacodynamic data suggest target exposures are achieved with preliminary clinical activity.