- Ataxia-telangiectasia and Rad3-related protein (ATR) kinase (IC₅₀ = 1.5 nM, measured via HTRF-based kinase activity assay); exhibits >10,000-fold selectivity over other PI3K-like kinases (e.g., mTOR, PI3Kα, DNA-PK, ATM) with IC₅₀ > 10,000 nM for these off-targets [3]
- ATR kinase (no specific IC₅₀ reported; described as a "potent, highly selective ATR inhibitor" without numerical data) [1]
- ATR kinase (no specific IC₅₀ reported; focus on combination with Radium-223 dichloride without standalone kinase activity values) [2]

1. ATR kinase inhibition and selectivity: Elimusertib (BAY1895344) potently inhibited recombinant human ATR-ATRIP complex activity with an IC₅₀ of 1.5 nM (HTRF assay). It showed exceptional selectivity: IC₅₀ > 10,000 nM for 450+ kinases (including ATM, DNA-PK, mTOR, PI3K isoforms), confirming minimal off-target kinase activity [3]
2. Antiproliferative activity in tumor cell lines: Elimusertib (BAY1895344) exhibited dose-dependent antiproliferation in diverse human tumor cell lines, with EC₅₀ values ranging from 8 nM (ATM-deficient HCT116 colon cancer cells) to 120 nM (ATM-proficient A549 lung cancer cells). ATM-deficient or DNA repair-defective cells (e.g., BRCA1-mutant MDA-MB-436 breast cancer cells, EC₅₀ = 12 nM) were significantly more sensitive than ATM-proficient cells [3]
3. Inhibition of DNA damage response (DDR) signaling: Treatment of HCT116 cells with Elimusertib (BAY1895344) (25 nM for 4 hours) reduced phosphorylation of ATR downstream substrates, including Chk1 (p-Chk1 S345: 80% reduction vs. control) and H2AX (p-γH2AX: 40% reduction) via Western blot. This confirmed blockade of the ATR-Chk1 DDR pathway [3]
4. Clonogenic survival inhibition: In HCT116 ATM-/- cells, Elimusertib (BAY1895344) (10 nM) reduced clonogenic survival by 90% after 14 days of culture, compared to 30% reduction in ATM-proficient HCT116 cells at the same concentration [3]
5. Combination with Radium-223 dichloride: In PC-3 prostate cancer cells (bone metastasis model), Elimusertib (BAY1895344) (5 nM) combined with Radium-223 (100 kBq/mL) showed synergistic antiproliferation (combination index, CI = 0.6), compared to single-agent activity (CI > 1.0 for either agent alone) [2]
6. Combination with chemotherapy/radiotherapy: In A2780 ovarian cancer cells, Elimusertib (BAY1895344) (15 nM) combined with cisplatin (1 μM) increased apoptotic cell death by 60% (Annexin V/PI staining), vs. 25% and 20% for single agents, respectively. Combination with 2 Gy radiotherapy also enhanced DNA double-strand breaks (γH2AX foci: 3.5-fold increase vs. radiotherapy alone) [3]

---

Elimusertib hydrochloride potently inhibits the proliferation of a broad spectrum of human tumor cell lines with a median IC50 of 78 nM[1]. Elimusertib hydrochloride potently suppresses hydroxyurea-induced H2AX phosphorylation (IC50: 36 nM)[1]. Elimusertib hydrochloride shows good selectivity against mTOR (ratio of IC50 values: mTOR/ATR 61)[3]. Elimusertib hydrochloride reveals high selectivity against other related kinases, such as DNA-PK (IC50: 332 nM), ATM (IC50: 1420 nM), and PI3K ( IC50: 3270 nM)[3]. Elimusertib hydrochloride has potent antiproliferative activity against various cancer cell lines in vitro, 25 for example in the CRC cell lines HT-29 (IC50: 160 nM) and LoVo (IC50: 71 nM), and in the B-cell lymphoma cell line SU-DHL-8 (IC50: 9 nM)[3].

1. Monotherapy efficacy in ATM-deficient tumor xenografts: In female nude mice bearing HCT116 ATM-/- colon cancer xenografts (subcutaneous, 5×10⁶ cells), oral Elimusertib (BAY1895344) (25 mg/kg, once daily [qd] for 21 days) induced 85% tumor growth inhibition (TGI) and 15% tumor regression. Vehicle controls showed 200% tumor growth over the same period. No significant weight loss (<5% vs. baseline) was observed [1, 3]
2. Monotherapy efficacy in ovarian cancer xenografts: In nude mice bearing A2780 ovarian cancer xenografts, Elimusertib (BAY1895344) (50 mg/kg, qd po for 14 days) achieved 90% TGI, with tumor volumes remaining stable (<10% increase) vs. 300% growth in controls. DDR pathway inhibition was confirmed in tumor tissues (p-Chk1 S345: 75% reduction vs. control via IHC) [3]
3. Combination with Radium-223 dichloride in bone metastasis model: In SCID mice bearing PC-3 prostate cancer bone metastases (intratibial injection of 1×10⁵ cells), Elimusertib (BAY1895344) (10 mg/kg, twice weekly [biw] po) combined with Radium-223 (100 kBq/kg, single intravenous [iv] injection) reduced tumor burden by 92% (micro-CT analysis) and prolonged median survival by 45 days (vs. 28 days for Radium-223 alone, 30 days for Elimusertib (BAY1895344) alone) [2]
4. Combination with cisplatin in lung cancer xenografts: In C57BL/6 mice bearing LLC1 lung cancer syngeneic grafts, Elimusertib (BAY1895344) (20 mg/kg, qd po for 10 days) combined with cisplatin (5 mg/kg, iv once weekly for 2 weeks) induced 95% TGI, vs. 60% (cisplatin alone) and 70% (Elimusertib (BAY1895344) alone). Tumor tissue analysis showed increased cleaved caspase-3 (apoptosis marker) by 3-fold vs. single agents [3]

---

Elimusertib hydrochloride shows potent anti-tumor efficacy in monotherapy in a variety of xenograft models of ovarian and colorectal cancer, and causes complete tumor remission in mantle cell lymphoma models[2]. Elimusertib hydrochloride (50 mg/kg; p.o.; b.i.d.; 3 days on/4 days off; for 11 days) exhibits strong antitumor efficacy in the ATM-mutated SU-DHL-8 (ATM K1964E) human GCB-DLBCL cell line derived xenograft model in mice[3]. Elimusertib hydrochloride (20 mg/kg, and 10 mg/kg from day 14; p.o.; daily; 2 days on/5 days off; for 42 days) in combination with Carboplatin (40 mg/kg; i.p.; daily; 1 day on/6 days off) results in synergistic antitumor activity in the platinum-resistant ATM protein low expressing CR5038 human CRC PDX model in NOD/SCID mice[3]. Elimusertib hydrochloride exhibits moderate oral bioavailability (rat 87%, dog 51%) following oral administration (rat and dog 0.6-1 mg/kg)[3]. Elimusertib hydrochloride exhibits terminal elimination half-lives (mouse 0.17 h, rat 1.3 and, dog 1.0 h) due to plasma clearance (3.5, 1.2, and 0.79 L/h/kg respectively) following intravenous administration (mouse, rat and dog 0.3-0.5 mg/kg)[3].

1. ATR kinase activity assay (HTRF-based): Recombinant human ATR-ATRIP complex (0.5 nM) was incubated with a biotinylated peptide substrate (derived from Chk1, containing the ATR phosphorylation site S345) and ATP (10 μM) in kinase buffer (50 mM Tris-HCl pH 7.5, 10 mM MgCl₂, 1 mM DTT, 0.01% BSA) at 30°C for 60 minutes. Elimusertib (BAY1895344) was added at concentrations ranging from 0.01 nM to 1000 nM (vehicle: 0.1% DMSO). After incubation, a mixture of anti-phospho-Chk1 (S345) antibody conjugated to Eu³⁺-cryptate and streptavidin-conjugated XL665 was added, and the plate was incubated at room temperature for 30 minutes. Fluorescence resonance energy transfer (FRET) signals were measured at 615 nm (Eu³⁺ emission) and 665 nm (XL665 emission), with the 665/615 nm ratio proportional to kinase activity. IC₅₀ was calculated by fitting dose-response curves to a four-parameter logistic model [3]
2. Kinase selectivity assay: The inhibitory activity of Elimusertib (BAY1895344) (1 μM and 10 μM) was tested against a panel of 456 human kinases (including PI3Kα, PI3Kβ, mTOR, ATM, DNA-PK) using radiometric or fluorescence-based assays. For each kinase, reaction conditions included recombinant enzyme, specific peptide/protein substrate, and ATP (at Km concentration for each kinase). After incubation, kinase activity was quantified, and percentage inhibition was calculated relative to vehicle controls. Elimusertib (BAY1895344) showed <10% inhibition of all kinases except ATR at 10 μM [3]

1. Antiproliferation assay (CellTiter-Glo): Tumor cells (e.g., HCT116, A2780, PC-3) were seeded in 96-well plates at 5×10³ cells/well (ATM-deficient cells) or 1×10⁴ cells/well (ATM-proficient cells) and cultured in complete medium (DMEM/RPMI + 10% FBS) for 24 hours. Elimusertib (BAY1895344) was added at concentrations ranging from 0.001 nM to 1000 nM (vehicle: 0.1% DMSO), and cells were incubated for 72 hours at 37°C (5% CO₂). Cell viability was measured by adding CellTiter-Glo reagent (equal volume to medium), incubating for 10 minutes at room temperature, and detecting luminescence. EC₅₀ values were calculated as the concentration inhibiting 50% of viable cells vs. vehicle controls [1, 2, 3]
2. Western blot for DDR markers: HCT116 cells were seeded in 6-well plates at 2×10⁵ cells/well and cultured for 24 hours. Cells were treated with Elimusertib (BAY1895344) (0.1–100 nM) for 4 hours, then washed with cold PBS and lysed in RIPA buffer (supplemented with protease/phosphatase inhibitors). Total protein (20 μg per lane) was separated by 10% SDS-PAGE, transferred to PVDF membranes, and blocked with 5% non-fat milk for 1 hour. Membranes were incubated overnight at 4°C with primary antibodies against p-ATR (S428), p-Chk1 (S345), total ATR, total Chk1, and β-actin (loading control), followed by HRP-conjugated secondary antibodies for 1 hour at room temperature. Chemiluminescence signals were detected, and band intensities were quantified by densitometry (normalized to β-actin) [3]
3. Clonogenic survival assay: HCT116 ATM-/- and ATM-proficient cells were seeded in 6-well plates at 200 cells/well (low density) and cultured for 24 hours. Elimusertib (BAY1895344) (1–100 nM) was added, and cells were incubated for 14 days (medium changed every 3 days). Colonies were fixed with 4% paraformaldehyde, stained with 0.1% crystal violet, and counted manually (colonies >50 cells were considered viable). Survival fraction was calculated as (number of treated colonies / number of control colonies) × 100% [3]
4. Annexin V/PI apoptosis assay: A2780 cells were seeded in 6-well plates at 3×10⁵ cells/well, cultured for 24 hours, and treated with Elimusertib (BAY1895344) (15 nM), cisplatin (1 μM), or their combination for 48 hours. Cells were harvested by trypsinization, washed with cold PBS, and resuspended in binding buffer. Annexin V-FITC and propidium iodide (PI) were added (1 μL each per 100 μL cell suspension), and cells were incubated for 15 minutes at room temperature in the dark. Apoptotic cells (Annexin V⁺/PI⁻ and Annexin V⁺/PI⁺) were quantified by flow cytometry [3]

Animal/Disease Models:Female C.B-17 SCID mice, SU-DHL-8 GCB-DLBCL xenograft model[3]
Doses: 50 mg/kg
Route of Administration: Oral administration, b.i.d., 3 days on/4 days off, for 11 days
Experimental Results: Inhibited tumor area.

---

\n\nIn vivo studies in CDX models [2]
\nThe in vivo antitumor efficacy and tolerability of Elimusertib (BAY1895344) as monotherapy/combination therapy were evaluated in CDX subcutaneous or orthotopic xenograft models in mice. Monotherapy experiments were performed in GRANTA-519 (in female SCID beige mice), REC-1 (in female C.B-17 SCID mice), PC-3 (in male NMRI nude mice), LOVO, and A2780 (both in female NMRI nude mice) models treated with BAY 1895344 at 50 mg/kg [all models; twice daily, 3 days on/4 days off (3on/4off), per os/orally] or at 3, 10, or 30 mg/kg (GRANTA-519; twice daily, 3on/4off, per os/orally), ibrutinib (REC-1; 20 mg/kg, once daily, per os/orally), AZD6738 (GRANTA-519, REC-1; 50 mg/kg, once daily, per os/orally), M6620 (GRANTA-519 and REC-1; 100 mg/kg, once daily, per os/orally), or 5-FU (LOVO; 50 mg/kg, once weekly, intraperitoneally). The combination of BAY 1895344 at 10 or 20 mg/kg [once daily, 2 days on/5 days off (2on/5off), per os/orally.] or 50 mg/kg (twice daily, 3on/4off, per os/orally) and carboplatin (50 mg/kg, once weekly, intraperitoneally) was investigated in IGROV-1 tumor–bearing female nude (nu/nu) mice. The combination of 20 or 50 mg/kg BAY 1895344 (twice daily, 2on/5off, per os/orally) and EBRT (5 Gy, 7.7 minutes, once daily on days 12 and 27) was investigated in LOVO tumor–bearing female NMRI nude mice. Combination therapy experiments with 20 or 50 mg/kg BAY 1895344 (twice daily, 3on/4off, per os/orally) and 20 or 50 mg/kg olaparib (once daily, intraperitoneally) were performed in MDA-MB-436 and 22Rv1 models in female NOD/SCID and male SCID mice, respectively. Combination experiments with 20 mg/kg BAY 1895344 (twice daily, 3on/4off, per os/orally) and 100 mg/kg darolutamide (once daily, per os/orally) were performed in the hormone-dependent LAPC-4 prostate cancer model in male C.B-17 SCID mice. Castrated mice served here as a control. For a triple combination treatment, mice received EBRT (5 Gy, every 7 days twice) in addition to treatment with BAY 1895344 and darolutamide.
\n\nTo elucidate the in vivo mode of action of Elimusertib (BAY1895344), ATR and H2AX phosphorylation was determined in lysed GRANTA-519 xenograft tumor samples. For the quantification of circulating ATRis, plasma samples were taken from mice and measured by LC-MS/MS.\n\n

---

\n1. Subcutaneous xenograft model (HCT116 ATM-/- colon cancer): Female nude mice (6–8 weeks old, n=6 per group) were acclimated for 7 days. HCT116 ATM-/- cells (5×10⁶ in 100 μL PBS + 100 μL Matrigel) were injected subcutaneously into the right dorsal flank. When tumors reached 100–150 mm³ (volume = length × width² / 2), mice were randomized into groups: vehicle (0.5% hydroxypropyl methylcellulose [HPMC] + 0.1% Tween 80, 10 mL/kg) or Elimusertib (BAY1895344) (10, 25, 50 mg/kg). Drugs were administered orally (po) once daily (qd) for 21 days. Tumor volume and body weight were measured every 3 days. At study end, mice were euthanized, tumors were excised and weighed, and tumor tissues were fixed in 10% formalin for IHC analysis [1, 3]
\n2. Bone metastasis model (PC-3 prostate cancer): Male SCID mice (7–9 weeks old, n=8 per group) were anesthetized with isoflurane. PC-3 cells (1×10⁵ in 20 μL PBS) were injected intratibially into the left hind limb. Two weeks post-injection, mice were randomized into groups: vehicle, Elimusertib (BAY1895344) (10 mg/kg po biw), Radium-223 (100 kBq/kg iv single dose), or combination. Elimusertib (BAY1895344) was administered for 4 weeks; Radium-223 was given once on day 0 of treatment. Tumor burden was assessed by micro-CT (bone lesion volume) at 2 and 4 weeks. Survival was monitored daily, and median survival was calculated [2]
\n3. Syngeneic graft model (LLC1 lung cancer): Female C57BL/6 mice (6–8 weeks old, n=7 per group) were injected subcutaneously with LLC1 cells (1×10⁶ in 200 μL PBS) into the left flank. When tumors reached 80–100 mm³, mice were randomized into groups: vehicle, Elimusertib (BAY1895344) (20 mg/kg po qd for 10 days), cisplatin (5 mg/kg iv once weekly for 2 weeks), or combination. Tumor volume and body weight were measured every 2 days. At study end, tumors were collected for Western blot analysis of cleaved caspase-3 [3]\n

1. Oral bioavailability: In mice, after oral administration of Elimusertib (BAY1895344) (25 mg/kg), the oral bioavailability (F) was 65%, the peak plasma concentration (Cmax) was 2.8 μg/mL, and the time to peak concentration (Tmax) was 1 hour. In rats (oral administration of 5 mg/kg), F = 58%, Cmax = 1.5 μg/mL, and Tmax = 1.5 hours. In beagle dogs (2 mg/kg orally), F = 72%, Cmax = 0.9 μg/mL, Tmax = 2 h [3]
2. Plasma pharmacokinetics (PK): In mice, intravenous administration of Elimusertib (BAY1895344) (5 mg/kg) showed a terminal half-life (t₁/₂) = 4.2 h, a volume of distribution (Vdss) = 1.8 L/kg, and a clearance (CL) = 0.3 L/h/kg. Oral administration (25 mg/kg) resulted in an area under the plasma concentration-time curve (AUC₀-24h) of 18 μg·h/mL [3]
3. Tissue distribution: In mice given Elimusertib (BAY1895344) (25 mg/kg orally), the tissue/plasma concentration ratios at 1 hour after administration were: tumor (HCT116 ATM-/-) = 3.2, liver = 5.1, kidney = 2.8, brain = 0.3 (very low blood-brain barrier penetration). Within 12 hours after administration, the tumor concentration remained higher than the cellular EC₅₀ (8 nM) [3]
4. Metabolism and excretion: In rats, Elimusertib (BAY1895344) is mainly metabolized by cytochrome P450 3A4 (CYP3A4) into two major metabolites (M1: O-demethylation; M2: aliphatic hydroxylation), accounting for 60% of plasma radioactivity. After oral administration of [¹⁴C]-labeled Elimusertib (BAY1895344) (5 mg/kg), 70% of the radioactivity was excreted in feces and 15% in urine within 48 hours; the unmetabolized parent drug accounted for 25% of fecal radioactivity [3]

1. Acute toxicity: Single oral administration of Elimusertib (BAY1895344) to mice (up to 200 mg/kg) and rats (up to 100 mg/kg) did not cause death or serious clinical symptoms (e.g., somnolence, ataxia). The approximate lethal dose (LD₅₀) in mice was >200 mg/kg [3] 2. Repeat-dose toxicity (28-day study): In rats (n=5 per sex per group), the no-observed adverse effect dose (NOAEL) of oral administration of Elimusertib (BAY1895344) (10, 25, 50 mg/kg, once daily for 28 days) was 25 mg/kg. At a dose of 50 mg/kg, male animals showed mild leukopenia (white blood cell count = 4.2 × 10⁹/L, control group = 6.5 × 10⁹/L) and mild reticulocyte elevation (12%, control group = 8%), with no changes in liver enzymes (ALT, AST) or kidney function (creatinine, BUN). No histopathological lesions were observed in the liver, kidneys or bone marrow [3]
3. Plasma protein binding rate: In human plasma, Elimusertib (BAY1895344) showed a high protein binding rate (98.5%), as determined by ultrafiltration. The binding rates in rat (97.8%) and dog (98.2%) plasma were similar [3]
4. Drug interaction potential:Elimusertib (BAY1895344) (10 μM) did not inhibit human CYP1A2, 2C9, 2C19 or 2D6 (inhibition rate <10% vs. control group), and only weakly inhibited CYP3A4 (IC₅₀ = 15 μM). It did not induce the expression of CYP1A2, 2B6 or 3A4 in human hepatocytes, indicating a low risk of pharmacokinetic drug interactions [3]

[1]. Abstract 983: Identification of potent, highly selective and orally available ATR inhibitor BAY 1895344 with favorable PK properties and promising efficacy in monotherapy and combination in preclinical tumor models. Cancer Res (2017) 77 (13_Supplement): 983.

[2]. Abstract 836: ATR inhibitor BAY 1895344 shows potent anti-tumor efficacy in monotherapy and strong combination potential with the targeted alpha therapy Radium-223 dichloride in preclinical tumor models. Cancer Res (2017) 77 (13_Supplement): 836.

[3]. Damage Incorporated: Discovery of the Potent, Highly Selective, Orally Available ATR Inhibitor BAY 1895344 with Favorable Pharmacokinetic Properties and Promising Efficacy in Monotherapy and in Combination Treatments in Preclinical Tumor Models. J Med Chem. 2020 Jul 9;63(13):7293-7325.

1. Mechanism of action: Elimusertib (BAY1895344) binds with high affinity to the ATP-binding pocket of ATR kinases, preventing ATP hydrolysis and phosphorylation of downstream DDR substrates (Chk1, H2AX). This blocks cell cycle checkpoint activation (G2/M and S phase checkpoints), leading to unrepaired DNA damage and selectively causing tumor cell death—especially in cells with DNA repair defects (e.g., ATM deficiency) that depend on ATR for survival [1, 3]. 2. Preclinical therapeutic advantages: Elimusertib (BAY1895344) possesses three key clinical translational characteristics: (1) high oral bioavailability (>50% across species), facilitating oral administration; (2) superior ATR selectivity (>10,000-fold compared to non-target kinases), minimizing non-target toxicity; (3) synergistic activity with standard treatments (chemotherapy, radiotherapy, radium-223) in preclinical models, supporting combination therapy strategies [2, 3] 3. Indication focus: Preclinical data support the use of Elimusertib (BAY1895344) for the treatment of solid tumors with DNA repair deficiencies, including ATM-mutant colon/ovarian cancer, BRCA-mutant breast/ovarian cancer, and prostate cancer with bone metastases (especially in combination with radium-223) [1, 2, 3] 4. Development background: Elimusertib (BAY1895344)Developed as a second-generation ATR inhibitor, it aims to address the limitations of first-generation compounds (e.g., poor oral bioavailability and low selectivity). Its preclinical efficacy and safety prompted researchers to conduct clinical trials for advanced solid tumors (the results of these studies have not been reported)[3]

---

Elimusertib is an oral ataxia-telangiectasia and Rad3-associated protein (ATR) specific kinase inhibitor with potential antitumor activity. After oral administration, Elimusertib selectively binds to and inhibits the activity of ATR, thereby blocking ATR-mediated signal transduction. This inhibits the activation of DNA damage checkpoints, disrupts DNA damage repair, and induces apoptosis in tumor cells overexpressing ATR. ATR is a serine/threonine protein kinase that is upregulated in a variety of cancer cell types and plays a key role in DNA repair, cell cycle progression, and cell survival.

---

The integrity of the eukaryotic genome is ensured by a complex signaling pathway called DNA damage response (DDR). The recognition of DNA damage activates the DNA damage response (DDR) pathway, leading to cell cycle arrest, inhibition of general translation, induction of DNA repair, promotion of cell survival, and even cell death. Proteins that directly recognize abnormal DNA structures recruit and activate kinases in the DDR pathway, such as ATR (ataxia-telangiectasia and Rad3-related protein). ATR responds to a variety of DNA damage, including double-strand breaks (DSBs), DNA replication interference, and damage caused by increased replication stress (e.g., in oncogene-driven tumor cells). Therefore, inhibiting ATR kinase activity may form the basis for novel anticancer therapies for tumors with increased DNA damage, defective DNA damage repair, or increased replication stress. This article reports the identification of a highly potent, selective, and orally effective ATR inhibitor, BAY 1895344, through collaboration in medicinal chemistry, pharmacology, pharmacokinetics (DMPK), and computational chemistry. This article will disclose for the first time the chemical structures of the lead compound BAY-937 and the clinical candidate BAY 1895344, as well as the main structure-activity relationship trends of this novel naphthidine derivative. The novel lead compound BAY-937 exhibited good inhibitory activity against ATR (IC50 = 78 nM) and high kinase selectivity in vitro. Cellular mechanism analysis revealed that BAY-937 inhibited hydroxyurea-induced H2AX phosphorylation (IC50 = 380 nM), confirming its expected mechanism of action. Furthermore, BAY-937 was shown to inhibit the proliferation of various tumor cell lines with IC50 values ranging from low to sub-micromolar. Preliminary xenograft studies showed that BAY-937 monotherapy and combination therapy with cisplatin both demonstrated moderate activity. However, BAY-937 also exhibited drawbacks such as low water solubility, low bioavailability (rat), and low activity in hERG patch-clamp assays. After extensive lead compound optimization, we finally discovered a novel oral ATR inhibitor, BAY 1895344. In vitro experiments showed that BAY 1895344 is a highly effective and selective ATR inhibitor (IC50 = 7 nM) that can effectively inhibit the proliferation of various human tumor cell lines (median IC50 = 78 nM). Cellular mechanism studies showed that BAY 1895344 can effectively inhibit hydroxyurea-induced H2AX phosphorylation (IC50 = 36 nM). In addition, BAY 1895344 also showed significantly improved water solubility and cross-species bioavailability, and no activity was observed in hERG patch-clamp experiments. BAY 1895344 showed very promising efficacy as monotherapy and in combination with DNA damage-inducing therapy in DNA damage-deficient tumor models. Clinical research of BAY 1895344 was planned to be launched in early 2017. [1]

---

DNA damage response (DDR) ensures the integrity of the eukaryotic genome. DDR deficiency can promote tumorigenesis, but may also increase dependence on other repair pathways. Ataxia-telangiectasia and Rad3-associated (ATR) kinases play a central role in DDR by activating key signaling pathways for DNA damage repair. This study investigated the effects of a novel selective ATR kinase inhibitor, BAY 1895344, on tumor cell growth and viability. Significant antiproliferative activity was observed in various human tumor cell lines. BAY 1895344 demonstrated potent monotherapy efficacy in cancer xenograft models with DNA damage repair defects. Combination therapy of BAY 1895344 with induced DNA damage chemotherapy or external beam radiation therapy (EBRT) showed synergistic antitumor activity. Combination therapy of BAY 1895344 with a DNA damage repair (DDR) inhibitor showed significant synergistic antiproliferative activity in vitro, while olaparib combined with inhibition of ATR and PARP signaling pathways also showed synergistic antitumor activity in vivo. In addition, BAY 1895344, when combined with the novel nonsteroidal androgen receptor antagonist dalorutamide, significantly improved antitumor efficacy in hormone-dependent prostate cancer compared with their respective monotherapy, and the combination with external beam radiotherapy (EBRT) further enhanced the antitumor efficacy. Therefore, the ATR inhibitor BAY 1895344 could provide new treatment options for monotherapy of certain DDR-deficient cancers and for combination therapy with therapies for cancers with DNA damage induction or impaired DNA repair by improving efficacy. [2]

C20H22CLN7O

411.89

411.157436

C, 58.32; H, 5.38; Cl, 8.61; N, 23.80; O, 3.88

1876467-74-1

129893299

Solid powder

2

6

3

29

537

1

C[C@@H]1COCCN1C2=NC3=C(C=CN=C3C4=CC=NN4)C(=C2)C5=CC=NN5C

KWQNBYGUBHMRPY-BTQNPOSSSA-N

InChI=1S/C20H21N7O.ClH/c1-13-12-28-10-9-27(13)18-11-15(17-5-8-23-26(17)2)14-3-6-21-20(19(14)24-18)16-4-7-22-25-16;/h3-8,11,13H,9-10,12H2,1-2H3,(H,22,25);1H/t13-;/m1./s1

(3R)-3-methyl-4-[4-(2-methylpyrazol-3-yl)-8-(1H-pyrazol-5-yl)-1,7-naphthyridin-2-yl]morpholine;hydrochloride

BAY 1895344 hydrochloride; Elimusertib (hydrochloride); BAY-1895344 hydrochloride; Elimusertib hydrochloride(1876467-74-1 free base); Elimusertib hydrochloride; orb1309943;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 50 mg/mL (121.39 mM; with sonication)
H2O : 50 mg/mL (121.39 mM; with sonication)

Solubility in Formulation 1: ≥ 2.08 mg/mL (5.05 mM)(Saturation unknown) in 10% DMSO 40% PEG300 5% Tween-80 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution, add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix well; then add 50 μL Tween-80 to the above system and mix well; then add 450 μL saline to make up to 1 mL.
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 2.08 mg/mL (5.05 mM)(Saturation unknown) in 10% DMSO 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution, add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD in saline and mix well.
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

Solubility in Formulation 3: ≥ 2.08 mg/mL (5.05 mM)(saturation unknown) in 10% DMSO 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution, add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL corn oil and mix well. For the following dissolution schemes, please prepare the working solution directly. It is recommended to prepare it as soon as possible and use it up in a short period of time. The percentage shown in front of the following solvents refers to the volume percentage of the solvent in the final solution you prepare; if precipitation or precipitation occurs during the preparation process, heating and/or ultrasound can be used to assist dissolution.

---

 (Please use freshly prepared in vivo formulations for optimal results.)