PARP1 ( IC50 = 0.57 nM )
In vitro activity: Talazoparib is a strong inhibitor of PARP1/2 (PARP1 IC50=0.57 nM); at concentrations up to 1 μM, it has no effect on PARG activity. With a dissociation constant (K_D) of 0.29 nM, talazoparib binds to PARP1. With K_is values of 1.20 and 0.85 nM, respectively, talazoparib inhibits PARP1 and -2 to a comparable degree. With 20–200 times more potency than current PARP1/2 inhibitors, talazoparib specifically targets tumor cells with BRCA1, BRCA2, or PTEN gene defects. The drug talazoparib targets tumor cells that have defects in homologous recombination genes. Both BRCA1-deficient tumor models (MX-1 and SUM149) and BRCA2-deficient tumor models (Capan-1) exhibit significant sensitivity to talazoparib. At concentrations as low as 100 pM, talazoparib induces nuclear γ-H2AX foci[1].

In vitro activity: Talazoparib is a strong inhibitor of PARP1/2 (PARP1 IC50=0.57 nM); at concentrations up to 1 μM, it has no effect on PARG activity. With a dissociation constant (K_D) of 0.29 nM, talazoparib binds to PARP1. With K_is values of 1.20 and 0.85 nM, respectively, talazoparib inhibits PARP1 and -2 to a comparable degree. With 20–200 times more potency than current PARP1/2 inhibitors, talazoparib specifically targets tumor cells with BRCA1, BRCA2, or PTEN gene defects. The drug talazoparib targets tumor cells that have defects in homologous recombination genes. Both BRCA1-deficient tumor models (MX-1 and SUM149) and BRCA2-deficient tumor models (Capan-1) exhibit significant sensitivity to talazoparib. At concentrations as low as 100 pM, talazoparib induces nuclear γ-H2AX foci[1].

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In a biochemical enzyme assay, Talazoparib tosylate (BMN 673) inhibited PARP1 with an IC50 of 0.57 nM, which was more potent than veliparib (4.73 nM), rucaparib (1.98 nM), and olaparib (1.94 nM). [1]
In a cellular assay measuring inhibition of hydrogen peroxide-induced poly (ADP-ribose) (PAR) synthesis in LoVo cells, Talazoparib tosylate had an EC50 of 2.5 nM, compared to 5.9 nM for veliparib, 4.7 nM for rucaparib, and 3.6 nM for olaparib. [1]
Talazoparib tosylate selectively killed tumor cells with homologous recombination (HR) defects. In the BRCA2-deficient pancreatic cancer cell line Capan-1, the single-agent cytotoxicity IC50 was 5 nM, compared to >10,000 nM for veliparib, 609 nM for rucaparib, and 259 nM for olaparib. [1]
In colony formation or 2D cytotoxicity assays across a panel of human tumor cell lines, Talazoparib tosylate showed remarkable potency in BRCA1-deficient (e.g., SUM149, SF50 = 8.57E-6 μM), BRCA2-deficient (e.g., Capan-1, SF50 = 0.005 μM), and PTEN-deficient models (e.g., MDA-MB-468, SF50 = 0.006 μM), while being less potent in HR-proficient models (e.g., MDA-MB-231, SF50 = 1.85 μM). The therapeutic window between BRCA-deficient and proficient cells was significantly greater for Talazoparib tosylate compared to other PARP inhibitors. [1]
In isogenic models of BRCA deficiency (mouse ES cells with BRCA1 defects and human DLD1 cells with BRCA2 knockout), Talazoparib tosylate selectively inhibited the growth of BRCA-deficient cells at much lower concentrations compared to veliparib, rucaparib, or olaparib. [1]
A parallel RNA interference screen in CAL51 cells using a library targeting 960 genes showed that the most profound sensitization to Talazoparib tosylate was caused by siRNAs targeting genes involved in HR/double-strand break repair (e.g., BRCA1, BRCA2, PALB2, ATM, ATR, CHEK1). The genetic sensitization profile was not significantly different from those of olaparib, rucaparib, or veliparib. [1]
Talazoparib tosylate induced DNA damage biomarkers at low concentrations. It induced nuclear γH2AX foci formation in cells at concentrations as low as 100 pM, whereas 100 nM of olaparib was required to elicit a similar response. [1]
Talazoparib tosylate potentiated the cytotoxicity of DNA-damaging agents. In combination with 200 μM temozolomide in LoVo cells, it resulted in 50% growth inhibition (GI50) at 3 nM. It also potentiated the effect of SN-38 (active metabolite of irinotecan) in MX-1 cells in a dose-dependent manner and showed additive effects with platinum drugs in vitro. [1]
Talazoparib tosylate (up to 1 μM) did not inhibit Poly (ADP-ribose) Glycohydrolase (PARG) activity. A broad off-target screening against receptors, ion channels, and enzymes at 10 μM showed no significant interaction. It did not significantly inhibit the hERG potassium channel at concentrations up to 100 μM. [1]

Talazoparib is easily absorbed through the mouth, exhibiting over 40% absolute oral bioavailability in rats when given carboxylmethyl cellulose as a dose. The oral administration of Talazoparib exhibits remarkable antitumor activity; mice treated with well-tolerated doses of Talazoparib showed profound sensitivity to xenografted tumors that carry defects in DNA repair caused by BRCA mutations or PTEN deficiency. Combining talazoparib with temozolomide, SN38, or platinum medications also has synergistic or additive antitumor effects[1].

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In nude mice bearing subcutaneous BRCA1-deficient MX-1 human mammary carcinoma xenografts, oral administration of Talazoparib tosylate once daily for 28 days at 0.33 mg/kg significantly inhibited tumor growth, with 4 out of 6 mice achieving a complete response (tumor impalpable). A lower dose of 0.1 mg/kg had a smaller effect but was still more effective than oral olaparib at 100 mg/kg once daily. [1]
A single oral dose of Talazoparib tosylate (1 mg/kg) in MX-1 xenograft-bearing mice drastically decreased intratumoral PAR levels at 2 and 8 hours post-administration, with partial recovery at 24 hours. [1]
In the MX-1 model, a twice-daily (BID) dosing regimen of Talazoparib tosylate (0.165 mg/kg/dose, BIDx28) resulted in complete responses in 6 out of 6 mice and prevented tumor re-establishment until the end of the study (8 weeks post-treatment), which was more effective than once-daily dosing (0.33 mg/kg/dose, QDx28). [1]
Talazoparib tosylate (0.33 mg/kg, oral, QDx28) also demonstrated anti-tumor activity in PTEN-null xenograft models (MDA-MB-468 and LNCap), causing significant tumor growth delay. [1]
Talazoparib tosylate potentiated the anti-tumor effects of cisplatin and carboplatin in MX-1 xenograft models. Oral Talazoparib tosylate administered once daily for 8 days in combination with a single intraperitoneal dose of cisplatin (6 mg/kg) showed dose-dependent sensitization. Combination with carboplatin (35 mg/kg, single i.p. dose) also resulted in significant potentiation of anti-tumor effect. [1]

Enzyme assays were carried out in 96-well FlashPlates with 0.5 U PARP1 enzyme, 0.25x activated DNA, 0.2 mCi [3H] NAD, and 5 mmol/L cold NAD (Sigma) in a final volume of 50 mL reaction buffer that contained 10% glycerol (v/v), 25 mmol/L HEPES, 12.5 mmol/L MgCl2, 50 mmol/L KCl, 1 mmol/L dithiothreitol (DTT), and 0.01% NP-40 (v/v), pH 7.6. NAD, either with or without inhibitors, was added to the PARP reaction mixture to start the reaction, which was then allowed to sit at room temperature for a minute. To halt the reaction, 50 microliter of ice-cold 20% trichloroacetic acid (TCA) was subsequently added to each well. Centrifugation took place after the plate was sealed and shaken for an additional 120 minutes at room temperature. Top-Count was used to identify the radioactive signal bound to the FlashPlate. Using the Michaelis–Menten equation, PARP1 Km was calculated for a range of substrate concentrations (1–100 mmol/L NAD). Utilizing the formula Ki ¼ IC50/[1þ (substrate)/Km], compound Ki was computed from the enzyme inhibition curve. The PARP2 enzyme Km and compound Ki were determined using the same assay protocol, with the exception of using 30 ng of PARP2, 0.25x activated DNA, 0.2 mCi [3H] NAD, and 20 mmol/L of cold NAD during the reaction's 30-minute room temperature duration.\n

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\nIn order to determine the PARP inhibitor Ki, enzyme assays were carried out in 96-well FlashPlate using 0.5 U PARP1 enzyme, 0.25x activated DNA, 0.2 mCi [3H] NAD, and 5 mmol/L cold NAD (Sigma) in a final volume of 50 mL reaction buffer that contained 10% glycerol (v/v), 25 mmol/L HEPES, 12.5 mmol/L MgCl2, 50 mmol/L KCl, 1 mmol/L dithiothreitol (DTT), and 0.01% NP-40 (v/v), and pH 7.6. NAD was added to the PARP reaction mixture, either with or without inhibitors, to start the reaction, and it was then incubated for one minute at room temperature. The reaction was then stopped by adding 50 microliter of ice-cold 20% trichloroacetic acid (TCA) to each well. After the plate was sealed and shaken for an additional 120 minutes at room temperature, centrifugation was performed. Top-Count was used to determine the radioactive signal bound to the FlashPlate. The Michaelis-Menten equation was used to calculate PARP1 Km at different substrate concentrations (ranging from 1 to 100 mmol/L NAD). Using the formula Ki ¼ IC50/[1þ (substrate)/Km], compound Ki was computed from the enzyme inhibition curve. Using the same assay protocol, Km for the PARP2 enzyme and compound Ki were found. However, instead of using 30 ng of PARP2, 0.25x activated DNA, 0.2 mCi [3H] NAD, and 20 mmol/L cold NAD, the reaction was run for 30 minutes at room temperature.

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\n\nPARP enzyme assays[1]
\nThe ability of a test compound to inhibit PARP-1 enzyme activity was assessed using Trevigen’s PARP Assay Kit following manufacturer’s instruction. IC50 values were calculated using GraphPad Prism5 software. For PARP inhibitor Ki determination, enzyme assays were carried out in 96-well FlashPlate with 0.5 unit PARP1 enzyme, 0.25x activated DNA (Trevigen), 0.2 μCi [3H] NAD and 5 μM cold NAD in a final volume of 50 μL reaction buffer containing 10%glycerol(v/v), 25 mM Hepes, 12.5 mM MgCl2, 50 mM KCl, 1 mM DTT and 0.01% NP-40(v/v), pH 7.6. Reactions were initiated by adding NAD to the PARP reaction mixture with or without inhibitors and incubated for 1 min at room temperature. 50 μL of ice-cold 20% TCA was then added to each well to stop the reaction. The plate was sealed and shaken for a further 120 min at RT, followed by centrifugation. Radioactive signal bound to the FlashPlate was determined using TopCount. PARP1 Km was determined using Michaelis–Menten equation from various substrate concentrations (1-100 μM NAD). Compound Ki was calculated from enzyme inhibition curve according to the formula: Ki = IC50/(1+[substrate]/Km). Km for PARP2 enzyme and compound Ki were determined with the same assay protocol except 30 ng PARP2, 0.25x activated DNA, 0.2 μCi [3H] NAD and 20 μM cold NAD were used in the reaction for 30min at room temperature.\n

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\nBiacore binding assay[1]
\nRecombinant human PARP1 (rhPARP1) catalytic domain (residues 662 – 1011) with N-terminal 6XHis-tag was generated in house and used in binding assay for PARP inhibitor interaction using Biacore T200 (GE Healthcare). rhPARP1 was immobilized on a CM5 sensor chip by amine coupling method. Briefly, one flow cell of a CM5 chip was first activated by a 7-min injection at 10 μL/min of freshly prepared 50 mM NHS: 200 mM EDC (1:1) at rate of 10 μL/min. Then rhPARP1 (100 μg/mL, in 10 mM MES pH 6.5) was injected onto the flow cell for 60-sec at 10 μL/min. The remaining active coupling sites were blocked with a 7-min injection of 1M ethanolamine at 10 μL/min. The immobilization buffer contains 10 mM Hepes pH 7.4, 150 mM NaCl, 0.05% Surfectant P20, 5 mM MgCl2, and 0.5 mM TCEP (tris(2-carboxyethyl)phosphine). The immobilization level was ~7600 RU. For binding kinetics measurement, PARP inhibitors at increasing concentrations (12.5, 25, 50, 100, 200 nM) were injected over the chip surface for 60 sec per injection. The exposure was followed by a dissociation phase of 3600 sec in running buffer (immobilization buffer + 1% DMSO) after the last injection. The flow rate was 50 μL/min. After sensorgrams were corrected for signals from a reference flow, kinetics was calculated with Biacore T200 evaluation software ver.1.0.\n

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\nIntracellular PAR formation assay[1]
\nCellular PAR synthesis assay assesses the ability of a test compound to inhibit polymerization of PAR. LoVo human colorectal tumor cells grown in 96-well microtiter plates overnight were pre-treated with increasing concentrations of PARP inhibitors for 30 min before H2O2 was added at a final concentration of 50 mM. After a 5-min treatment at room temperature, cells were fixed for 10 minutes with pre-chilled methanol/acetone(7:3) at −20 °C. Fixed cells were incubated with anti-PAR monoclonal antibody for 60 min, followed by incubation with FITC coupled goat anti-mouse IgG (diluted 1:100) and 1 μg/mL DAPI for 60 min. FITC signal was normalized with DAPI signal, and EC50 values were calculated using GraphPad Prism.\n

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PARP Enzyme Inhibition Assay: The ability of test compounds to inhibit PARP1 enzyme activity was assessed using a commercial PARP assay kit. Reactions typically contained PARP1 enzyme, activated DNA, NAD (including radiolabeled [³H]NAD), and test compounds in a reaction buffer. After incubation (e.g., 1 minute at room temperature for PARP1), the reaction was stopped with trichloroacetic acid (TCA). Radioactive signal bound to the plate was determined by scintillation counting. IC50 values were calculated from dose-response curves. For Ki determination, assays were performed with varying NAD concentrations to determine Km, and Ki was calculated using the formula Ki = IC50/(1+[substrate]/Km). A similar protocol with PARP2 enzyme was used for PARP2 Ki determination. [1]
Biacore Binding Assay (Surface Plasmon Resonance):The recombinant human PARP1 catalytic domain was immobilized on a CMS sensor chip via amine coupling. Test compounds (Talazoparib tosylate, veliparib) at increasing concentrations (12.5, 25, 50, 100, 200 nM) were injected over the chip surface for 60 seconds per injection, followed by a long dissociation phase in running buffer. Sensorgrams were corrected using a reference flow cell. Binding kinetics (on-rate, off-rate) and the dissociation constant (K_D) were calculated using evaluation software. [1]

For five days, temozolomide (TMZ) and talazoparib (10, 40 nM) are administered either alone or in combination to LoVo cells. CellTiter-Glo assay is used to determine the survivability fraction. [1] A panel of 11 SCLC cell lines (IC50=1.7 to 15 nmol/L), all of which fall within clinically feasible ranges, demonstrate Talazoparib (BMN 673; MDV3800) 's strong inhibitory action. Furthermore, PI3K pathway activity and DNA repair protein expression are correlated with Talazoparib (BMN 673; MDV3800)  sensitivity.

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Confocal microscopy[1]
Cells were seeded on coverslips placed in 6-well plates and after 24 hours treated with several concentrations of olaparib or Talazoparib (BMN 673; MDV3800). 24 hours after treatment the cells were fixed in 10% formalin (3.7% PFA) for 1 hour. Cells were permeabilized with 0.2% Triton X-100 in PBS for 20 minutes, treated with 50 μL DNase I (diluted 1/10 in PBS) for 1 hour at 37°C and then blocked with IFF (PBS + 1% BSA and 2% FBS followed by filter sterilization) for 1 hour. The coverslips were then incubated with rabbit anti-γH2Ax primary (Millipore) and mouse anti-RAD51 primary (both 1:1000 in 50μL IFF) overnight at 4°C. The next day cells were incubated with anti-mouse Alexafluor 546 secondary and anti-rabbit Alexafluor 488 secondary (both 1:1000 in 50μL IFF) for one hour. Cells were then washed in PBS containing DAPI 1:10.000 for 10 minutes and attached on glass plates using Vectashield and nail polish. A minimum of four pictures were made of each coverslip using the Leica confocal microscope, and cells were subsequently counted. At least 100 cells were assessed per coverslip, being positive for γH2Ax if they had more than 5 foci per nucleus. The percentage of positive cells was plotted.

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Intracellular PAR Formation Assay: LoVo human colorectal tumor cells grown in 96-well plates were pre-treated with increasing concentrations of PARP inhibitors for 30 minutes. PAR synthesis was then induced by adding hydrogen peroxide (final concentration 50 mM) for 5 minutes at room temperature. Cells were fixed, permeabilized, and incubated with an anti-PAR monoclonal antibody, followed by a FITC-conjugated secondary antibody and DAPI staining. FITC signal (PAR) was normalized to DAPI signal (DNA/nuclei), and EC50 values were calculated from dose-response curves. [1]
Colony Formation (Clonogenic) Survival Assays: Cells were seeded at low density (500-2000 cells/well) in 6-well plates. After 24 hours, media was replaced with fresh media containing the PARP inhibitor. Media with inhibitor was refreshed twice weekly for 14 days. Colonies were then fixed with trichloroacetic acid, stained with sulforhodamine B, counted, and normalized to vehicle-treated controls to calculate Surviving Fractions. [1]
Single Agent Cytotoxicity and Chemo-sensitization Assays (2D): For single-agent cytotoxicity, cells were seeded in 96-well plates at a density allowing linear growth for 10-12 days. Cells were treated with increasing concentrations of PARP inhibitors for 10-12 consecutive days (media changed every 5 days). Cell survival was determined using a luminescent cell viability assay and expressed relative to mock-treated controls. IC50 or GI50 values were calculated. For chemo-sensitization assays, PARP inhibitors at various concentrations were combined with a fixed concentration of a cytotoxic agent (e.g., 200 μM temozolomide for LoVo cells, or a range of SN-38 concentrations for MX-1 cells) for 5 days, followed by cell viability measurement. [1]
siRNA Screen:CAL51 cells plated in 96-well plates were transfected with a siRNA library (final concentration 100 nM) targeting 960 genes. At 48 hours post-transfection, cells were treated with PARP inhibitors at their respective SF80 concentrations or vehicle (DMSO) for 5 days. Cell viability was assessed using a luminescent assay. Data was analyzed to calculate a Drug Effect (DE) Z score for each siRNA, identifying genes whose silencing sensitized cells to the drug. [1]
Immunofluorescence for γH2AX Foci: Cells seeded on coverslips were treated with PARP inhibitors for 24 hours, fixed, permeabilized, and treated with DNase I. After blocking, cells were incubated overnight at 4°C with primary antibodies against γH2AX and RAD51. After washing, cells were incubated with fluorescent dye-conjugated secondary antibodies and DAPI. Images were acquired by confocal microscopy. Cells with more than 5 γH2AX foci per nucleus were counted as positive. [1]

Mice: In single-agent trials, oral gavage (per os) is used to deliver olaparib (100 mg/kg), Talazoparib (0.33 or 0.1 mg/kg/d), or vehicle (10% DMAc, 6% Solutol, and 84% PBS) once daily or twice daily, respectively, for a total of 28 days. After the final dosage day, mice are observed every day for an additional 10 days[1]. \nXenograft experiments[1]
\nFemale athymic nu/nu mice (8-10 week old) were used for all in vivo xenograft studies. Mice were quarantined for at least 1 week before experimental manipulation. Exponentially growing cells (LNcap, MDA-MB-468) or in vivo passaged tumor fragments (MX-1) were implanted subcutaneously at the right flank of nude mice. When tumors reached an average volume of ~150 mm3, mice were randomized into various treatment groups (6-8 mice/group) in each study. Mice were visually observed daily and tumors were measured twice weekly by calliper to determine tumor volume using the formula [length/2] × [width2]. Group median tumor volume (mm3) was graphed over time to monitor tumor growth. In single agent studies, olaparib (100mg/kg), Talazoparib (BMN 673; MDV3800)  (various doses as indicated), or vehicle (10% DMAc, 6% Solutol and 84% PBS) was administered by oral gavage (p.o.), once daily or Talazoparib (BMN 673; MDV3800)  (0.165 mg/kg) twice daily for 28 consecutive days. Mice were continuously monitored for 10 more days after last day of dosing. In cisplatin combination study, Talazoparib (BMN 673; MDV3800) , olaparib, or vehicle was administered p.o. once daily for 8 days starting on day 1. Cisplatin at a dosage of 6 mg/kg or its vehicle (saline) was administered intra-peritoneally (i.p) as a single injection on day 3, 30 minutes after PARP inhibitor was administered. Combination with carboplatin was conducted in a similar way in MX-1 model in which Talazoparib (BMN 673; MDV3800)  was administered p.o. once daily for either 8 days or 5 days and carboplatin was injected i.p. at single dose of 35 mg/kg, 30 min after Talazoparib (BMN 673; MDV3800)  on day 3.[1]

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\nPAR assay in vivo[1]
\nMX-1 tumor xenografts were prepared as described in methods. When tumors reached an average volume of ~150 mm3, olaparib (100 mg/kg), Talazoparib (BMN 673; MDV3800)  (1 mg/kg) or vehicle was administered in a single p.o. dosing. Tumors were harvested at 2, 8 and 24 hours after drug dosing, snap frozen in liquid N2. Tumor tissue was then homogenized in PBS on ice and extracted with lysis buffer (25mM Tris pH 8.0, 150mM NaCl, 5mM EDTA, 2mM EGTA, 25mM NaF, 2mM Na3VO4, 1mM Pefabloc, 1% Triton X-100, and protease inhibitor cocktail) containing 1% SDS. Levels of PAR in the tumor lysates were determined by ELISA using PARP in vivo PD Assay II kit.

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\nSingle-Agent Efficacy in Xenograft Models: Female athymic nu/nu mice (8-10 weeks old) were implanted subcutaneously with tumor cells (e.g., LNcap, MDA-MB-468) or tumor fragments (MX-1). When tumors reached an average volume of ~150 mm³, mice were randomized into treatment groups. Talazoparib tosylate (BMN 673) was administered orally by gavage (p.o.) at specified doses (e.g., 0.1, 0.33 mg/kg) once daily (QD) or twice daily (BID, e.g., 0.165 mg/kg/dose) for 28 consecutive days. Olaparib (100 mg/kg, p.o., QD) or vehicle (10% DMAc, 6% Solutol, 84% PBS) served as controls. Tumor volumes were measured twice weekly. [1]
\nPharmacodynamic (PAR Inhibition) Study in Xenografts:Mice bearing MX-1 xenografts received a single oral dose of Talazoparib tosylate (1 mg/kg), olaparib (100 mg/kg), or vehicle. Tumors were harvested at 2, 8, and 24 hours post-dose, snap-frozen, homogenized, and lysed. PAR levels in tumor lysates were quantified using a commercial ELISA kit. [1]
\nCombination Therapy with DNA-Damaging Agents:For combination with cisplatin, Talazoparib tosylate or vehicle was administered p.o. once daily for 8 days starting on day 1. Cisplatin (6 mg/kg) or saline vehicle was administered intraperitoneally (i.p.) as a single injection on day 3, 30 minutes after the PARP inhibitor. For combination with carboplatin, a similar schedule was used where Talazoparib tosylate was given p.o. once daily for 5 or 8 days and carboplatin (35 mg/kg, single i.p. dose) was administered 30 minutes after the PARP inhibitor on day 3. Tumor growth and animal body weight were monitored. [1]

Absorption, Distribution and Excretion
Following a once-daily oral administration of 1 mg taprazole, the mean [coefficient of variation (CV%)] AUC and peak plasma concentration (Cmax) at steady state were 208 (37%) ng·hr/mL and 16.4 (32%) ng/mL, respectively. The mean (CV%) steady-state trough concentration (Ctrough) was 3.53 (61%) ng/mL. Steady state was reached within 2 to 3 weeks of treatment. The time to peak concentration (Tmax) was 1 to 2 hours. High-fat, high-calorie diets increased the mean Cmax by 46% and the median Tmax by 4 hours from 1 hour, but did not affect the AUC. The primary route of excretion is renal. Approximately 68.7% of the total dose of radiolabeled taprazole was recovered in the urine, of which 54.6% was unchanged. Approximately 19.7% was recovered in the feces, of which 13.6% was unchanged.
The mean apparent volume of distribution of taporani is 420 L.
The mean apparent oral clearance is 6.45 L/h. The inter-individual variability is 31%.
Metabolism/Metabolites
Taporani is minimally metabolized in the liver. Metabolic pathways include monooxidation, dehydrogenation, monodefluorination of taporani via cysteine conjugation, and glucuronide conjugation.
Biological Half-Life
The mean terminal plasma half-life (± standard deviation) in cancer patients is 90 (±58) hours.
In vitro metabolic studies in rat, dog, and human liver microsomes showed that taporani tosylate has excellent metabolic stability, with over 90% of the compound remaining after incubation at 1 μM concentration for 2 hours. [1]
In rat pharmacokinetic studies, tapazoni tosylate, when administered in 0.5% carboxymethyl cellulose solution, had an absolute oral bioavailability of >40%. [1]
Tapazoni tosylate at concentrations up to 10 μM did not inhibit the five major human hepatic cytochrome P450 enzymes (CYP1A2, 2C9, 2C19, 2D6, and 3A4). [1]

Hepatotoxicity
Elevated serum transaminase levels are common during tprazole treatment, occurring in 33% of patients, but only 1% had transaminase levels exceeding 5 times the upper limit of normal. These elevations are usually transient and without symptoms or jaundice. Similar rates of transaminase elevation were also reported in the control and comparison groups. Clinical use of tprazole is limited, and no cases of acute liver injury with symptoms or jaundice have been identified. Due to limited clinical experience with tprazole and other PARP inhibitors, the likelihood of liver injury is unclear. Probability score: E (Unproven, but suspected cause of clinically significant liver injury). Pregnancy and Lactation Effects ◉ Overview of Use During Lactation There is currently no information regarding the clinical use of tprazole during lactation. Because tprazole binds to plasma proteins at a rate of 74%, its concentration in breast milk is likely to be low. The manufacturer recommends discontinuing breastfeeding during taprazole treatment and for one month after the last dose.
◉ Effects on breastfed infants
No published information found as of the revision date.
◉ Effects on lactation and breast milk
No published information found as of the revision date.

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Protein binding
In vitro studies showed that taprazole had a protein binding rate of 74%, independent of taprazole concentration.

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In the MX-1 xenograft model, oral administration of 0.33 mg/kg and 0.1 mg/kg of taprazole tosylate once daily for 28 days was well tolerated, with no animal deaths or significant weight loss observed. [1]
In studies using taprazole tosylate in combination with cisplatin, the combination of taprazole tosylate and cisplatin resulted in moderate, dose-dependent weight loss. Following treatment with cisplatin at doses of 1, 0.33, 0.1, and 0.033 mg/kg, the mean maximum weight loss was 11%, 6%, 5%, and 3%, respectively (compared to 3% in the cisplatin-only group). One animal died on day 20 in the 1 mg/kg tapazoni tosylate plus cisplatin group. Most animals returned to normal weight at the end of treatment. [1]
In the MX-1 model, with twice-daily administration (0.165 mg/kg/dose, BIDx28), one in six mice experienced a significant weight loss (>20%) and was sacrificed on day 53. All other animals in this study tolerated the treatment well. [1]
In vitro, no significant inhibition of hERG potassium channels was observed at concentrations up to 100 μM, suggesting a low clinical risk of cardiac QTc interval prolongation. [1]

[1]. BMN 673, a novel and highly potent PARP1/2 inhibitor for the treatment of human cancers with DNA repair deficiency. Clin Cancer Res. 2013 Sep 15;19(18):5003-15.

Tolapzopanib tosylate is the tosylate form of tolapzopanib, a highly bioavailable, orally bioavailable ribozyme polymerase (PARP) inhibitor with potential antitumor activity. After administration, tolapzopanib selectively binds to PARP, blocking the PARP-mediated base excision repair pathway for single-strand DNA breaks. This leads to the accumulation of DNA strand breaks, promoting genomic instability and ultimately resulting in apoptosis. PARP catalyzes post-translational ADP-ribosylation of nucleoproteins, which signal and recruit other proteins to repair damaged DNA and are activated by single-strand DNA breaks.
See also: Tapzopanib (containing the active moiety).
Indications
Talzenna is indicated for monotherapy in adult patients with germline BRCA1/2 mutations and HER2-negative locally advanced or metastatic breast cancer. Unless the patient is unsuitable for anthracycline and/or taxane therapy, they should have received these drugs in (neo)adjuvant, locally advanced, or metastatic treatment. Hormone receptor (HR)-positive breast cancer patients should have received endocrine therapy or be considered unsuitable for it.

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Tprazole is an oral small-molecule DNA repair enzyme, poly(ADP-ribose) polymerase (PARP), used to treat certain cases of breast cancer. Elevated serum transaminases during tprazole treatment have a moderate incidence and are suspected to cause rare, clinically significant acute liver injury.
Tprazole is an inhibitor of mammalian poly(ADP-ribose) polymerase (PARP), an enzyme responsible for regulating important cellular functions such as DNA transcription and DNA repair. Developed by Pfizer, tprazole was first approved by the U.S. Food and Drug Administration (FDA) in October 2018 and by the European Medicines Agency (EMA) in June 2019. In September 2020, tprazole was approved by Health Canada. Currently, tprazole is used to treat BRCA-mutated breast cancer and HRR-mutated prostate cancer. Tprazole is a poly(ADP-ribose) polymerase inhibitor. Its mechanism of action is as a poly(ADP-ribose) polymerase inhibitor. Tprazole is an orally administered small-molecule DNA repair enzyme, poly(ADP-ribose) polymerase (PARP), an anti-tumor drug used to treat certain types of breast cancer. Elevated serum transaminases are moderately common during tprazole treatment, and it may cause rare, clinically significant acute liver injury. Tprazole is an orally bioavailable poly(ADP-ribose) polymerase (PARP) inhibitor with potential anti-tumor activity. Tprazole selectively binds to PARP, blocking the PARP-mediated base excision repair pathway to repair single-strand DNA breaks. This exacerbates the accumulation of DNA strand breaks, promotes genomic instability, and ultimately leads to apoptosis. PARP catalyzes post-translational ADP ribosylation of nucleoproteins, which signal and recruit other proteins to repair damaged DNA and are activated by single-strand DNA breaks. See also: Talazopanib tosylate (active ingredient). Drug Indications Talazopanib is indicated for the treatment of adult patients with locally advanced or metastatic breast cancer who have pathogenic or suspected pathogenic germline BRCA mutations (gBRCAm) and are HER2-negative. This indication is approved by the US FDA, EMA, and Health Canada. In the United States, talazopanib is also used in combination with enzalutamide for the treatment of adult patients with metastatic castration-resistant prostate cancer (mCRPC) who have HRR gene mutations. Talazopanib monotherapy is also indicated for the treatment of adult patients with locally advanced or metastatic breast cancer who have germline BRCA1/2 mutations and are HER2-negative. Unless the patient is unsuitable for anthracycline and/or taxane therapy, the patient should have received these drugs during (neo)adjuvant, locally advanced, or metastatic treatment. Hormone receptor (HR)-positive breast cancer patients should have received endocrine therapy or be considered unsuitable for it.
Treatment of Ewing's sarcoma
Treatment of breast cancer, treatment of prostate cancer
Mechanism of Action
Poly(ADP-ribose) polymerase (PARP) is a multifunctional enzyme involved in important cellular functions such as DNA transcription and DNA repair. PARP recognizes and repairs single-strand breaks (SSBs) in DNA via the base excision repair (BER) pathway. Double-strand breaks (DSBs) in DNA are repaired via homologous recombination mediated by tumor suppressor proteins encoded by BRCA1 and BRCA2. Tapazanib is a potent inhibitor of poly(ADP-ribose) polymerase (PARP), including PARP1 and PARP2. In vitro studies have shown that tapazanib has similar affinity to PARP-1 and PARP-2 subtypes. Tprazole panib inhibits the base excision repair (BER) pathway, leading to the accumulation of unrepaired single-strand breaks (SSBs) and subsequent double-strand breaks (DSBs), the most toxic form of DNA damage. While BRCA-dependent homologous recombination (HR) can repair DSBs in normal cells, this repair pathway is defective in cells carrying BRCA1/2 mutations, such as certain tumor cells. Inhibition of PARP in cancer cells carrying BRCA mutations leads to genomic instability and apoptosis. This end result, also known as synthetic lethality, refers to the fact that the two defects—PARP activity inhibition and HR-mediated loss of DSB repair—are harmless individually but combine to cause detrimental consequences. By inhibiting PARP, tprazole panib increases the formation of PARP-DNA complexes, resulting in DNA damage, reduced cell proliferation, and apoptosis. Tprazole panib tosylate (BMN 673) is a novel, potent, and selective PARP1 and PARP2 inhibitor with good metabolic stability, oral bioavailability, and pharmacokinetic properties. [1]
This drug utilizes the principle of synthetic lethality to selectively kill cancer cells with defects in homologous recombination DNA repair, such as cancer cells carrying BRCA1, BRCA2, or PTEN mutations. [1]
Its chemical name is (8S,9R)-5-fluoro-8-(4-fluorophenyl)-9-(1-methyl-1H-1,2,4-triazol-5-yl)-8,9-dihydro-2H-pyrido[4,3,2-de]phthalazine-3(7H)-one. It is one of the trans isomers (LT-00673) derived from the racemic LT-00628. Another trans isomer (LT-00674) and the cis isomer have much lower activity. [1]
The potent antitumor activity of tprazole panitin tosylate is closely related to its PARP inhibitory activity, which was confirmed by chiral selectivity studies comparing it with the less active isomers. [1]
This drug was in the early stages of clinical development when it was published, and is currently undergoing Phase I clinical trials for patients with advanced cancers and advanced hematologic malignancies with defects in DNA repair pathways. [1]

C26H22F2N6O4S

552.56

552.139

C, 56.52; H, 4.01; F, 6.88; N, 15.21; O, 11.58; S, 5.80

1373431-65-2

1207454-56-5 (racemic); 1207456-01-6; 1373431-65-2

135565654

White to off-white solid powder

4.22

3

10

3

39

861

2

S(C1C=CC(C)=CC=1)(=O)(=O)O.FC1C=C2C(NN=C3C2=C(C=1)N[C@H](C1C=CC(=CC=1)F)[C@H]3C1=NC=NN1C)=O

QUQKKHBYEFLEHK-QNBGGDODSA-N

InChI=1S/C19H14F2N6O.C7H8O3S/c1-27-18(22-8-23-27)15-16(9-2-4-10(20)5-3-9)24-13-7-11(21)6-12-14(13)17(15)25-26-19(12)28;1-6-2-4-7(5-3-6)11(8,9)10/h2-8,15-16,24H,1H3,(H,26,28);2-5H,1H3,(H,8,9,10)/t15-,16-;/m1./s1

(11S,12R)-7-fluoro-11-(4-fluorophenyl)-12-(2-methyl-1,2,4-triazol-3-yl)-2,3,10-triazatricyclo[7.3.1.05,13]trideca-1,5(13),6,8-tetraen-4-one;4-methylbenzenesulfonic acid

BMN 673 tosylate; BMN673; BMN-673; UNII-02WK9U5NZC; 02WK9U5NZC; Talazoparib tosylate [USAN]; LT673 tosylate; LT 673; LT-673 tosylate; MDV-3800 tosylate; MDV 3800; MDV3800 tosylate; trade name: Talzenna

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)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.52 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 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 is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.52 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 is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 3: 5%DMSO+ 40%PEG300+ 5%Tween 80+ 50%ddH2O: 2.5mg/ml (6.57mM)

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