p53-MDM2 (IC50 = 6 nM)
RG7388 (Idasanutlin): Proto-Oncogene Proteins c-mdm2 (MDM2)-Tumor Suppressor Protein p53 interaction (potent and selective inhibition) [1]
RG7388 (Idasanutlin): Proto-Oncogene Proteins c-mdm2 (MDM2) [2]
Idasanutlin (RG7388): Proto-Oncogene Proteins c-mdm2 (MDM2) (oral MDM2 antagonist, inhibits p53-MDM2 interaction) [3]

In cancer cells expressing wild-type p53, isasanutlin inhibits cell proliferation with an IC50 of 30 nM and induces dose-dependent p53 stabilization, cell cycle arrest, as well as cell apoptosis.[1]
RG7388 displayed improved in vitro binding as well as cellular potency/selectivity. Thus, compound 12 was chosen for further studies. In cell-based mechanistic studies), RG7388 induced dose-dependent p53 stabilization, cell cycle arrest, and apoptosis in cancer cells expressing wild-type p53, consistent with a nongenotoxic p53 activation mechanism.[1]

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RG7388-induced apoptosis in SJSA osteosarcoma cells is delayed relative to drug exposure but does not require continuous treatment[2].

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1. RG7388 is a second-generation small-molecule p53-MDM2 inhibitor with superior potency and selectivity compared to the first-generation inhibitor RG7112 [1]
2. RG7388-induced apoptosis in tumor cells was delayed relative to drug exposure, and continuous drug treatment was not required to trigger the apoptotic effect [2]
3. Idasanutlin (RG7388) exhibited dose- and schedule-dependent p53 activation in in vitro assays; its anti-proliferative effects were evaluated, and MIC-1 levels were found to increase in an exposure-dependent manner with once-daily (QD) dosing [3]

In initial efficacy testing, daily dosing at 30 mg/kg and twice a week dosing at 50 mg/kg of RG7388 were statistically equivalent in our tumor model. In addition, weekly dosing of 50 mg/kg was equivalent to 10 mg/kg given daily. The implementation of modeling and simulation on these data suggested several possible intermittent clinical dosing schedules. Further preclinical analyses confirmed these schedules as viable options.[2]

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RG7388 also achieved impressive in vivo efficacy against established human SJSA1 osterosarcoma xenografts in nude mice at significantly lower doses and exposures compared to RG7112[1].

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1. RG7388 activated p53, inhibited tumor growth and improved survival in xenograft models [3]
2. In a mouse osteosarcoma xenograft model, daily dosing of RG7388 at 30 mg/kg and twice-weekly dosing at 50 mg/kg showed statistically equivalent antitumor activity; weekly dosing of 50 mg/kg was also equivalent to daily dosing of 10 mg/kg [2]
3. A pharmacokinetic-pharmacodynamic (PKPD) model based on RG7388 data in the mouse osteosarcoma xenograft model predicted that intermittent dosing regimens could achieve tumor stasis, which was verified by subsequent preclinical analyses [2]

The 50 mM Tris-HCl, pH 7.4, 100 mM NaCl, 1 mM DTT, and 0.02 or 0.2 mg/ml BSA buffer is used for the p53-MDM2 HTRF assay. Aliquots of small-molecule inhibitors are kept at 4°C in 96-deep-well plates as stock solutions of 10 mM DMSO. Just before testing, it is thawed and blended. A biotinylated p53 peptide and GST-MDM2 are incubated with the substance for an hour at 37°C. Following the addition of Eu-8044-streptavidin and Phycolink goat anti-GST (Type 1) allophycocyanin, an hour-long incubation at room temperature is required. Using the Envision fluorescence reader, plates are read. Data sets in duplicate or triplicate between plates are used to calculate IC50 values. Data is analyzed by XLfit4 (Microsoft) using a Sigmoidal Dose-Response Model with 4 Parameter Logistic Model and the equation Y= (A+ ((B-A)/ (1+ ((C/x)^D)))), where A and B are enzyme activity in the absence or presence of infinite inhibitor compound, respectively, C is the IC50, and D is the Hill coefficient.[1]

Tetrazolium dye assay is used to assess cell proliferation. The linear regression of a plot of the concentration versus percent inhibition's logarithm yields the concentration at which cell proliferation is 50% (IC50) or 90% (IC90) inhibited.[1]

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In vitro testing in cancer cell lines[2]
RG7388 was prepared at concentrations of 1 and 10 mmol/L in DMSO and stored in aliquots at −20°C. SJSA, RKO, HCT116, H460, A375, SK-MEL-5, SW480, MDA435, and HeLa cells were obtained from the ATCC. Cell lines were authenticated by short tandem repeat analysis through Promega authentication services. For in vitro studies, cells were cultured in their ATCC-designated media. Medium was supplemented with 10% FBS and 1% 200 nmol/L l-glutamine. To assess cell viability, cells were seeded at densities identified for best growth for a 5-day assay in 96-well plates in normal growth media. Serial dilutions of RG7388 (1–3 in fresh media) starting at 300 μmol/L were applied to wells (1–10) in triplicate for a final concentration range of 0.01 to 30 μmol/L and control wells were treated with 0.3% DMSO equivalent to DMSO at the highest RG7388 concentration. Cell respiration, as an indicator of cell viability, was measured by the reduction of MTT to formazan as previously described.
Percent apoptosis was determined as described in Tovar and colleagues. For Western blot analysis, cells were cultured in T-75 flasks (4 mL total volume at 5 × 105 cells/well) and incubated overnight at 37°C, 5% CO2. Cells were treated with 0.3 or 1.8 μmol/L of RG7388 or 0.1% DMSO as control. Treatment duration was 16 hours, and lysates were prepared before washout and at 4, 8, 24, and 48 hours after RG7388 washout.

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1. To assess the anti-proliferative effects and p53 activation of Idasanutlin (RG7388), in vitro cell-based assays were performed to detect the expression of biomarkers (e.g., MIC-1) and evaluate the drug’s anti-proliferative activity under different dosing schedules; the correlation between drug exposure and p53 activation was also analyzed [3]
2. To study the apoptotic effect of RG7388, tumor cell lines were treated with the drug, and the time-course of apoptosis was monitored to determine the relationship between drug exposure and the onset of apoptosis [2]

Formulated in 30% drug substance and 70% hydroxypropyl methylcellulose acetate succinate polymer; 25 mg/kg; p.o.
Athymic female nude mice (Crl:NU-Foxn1nu) bearing SJSA human osteosarcoma xenograft model Efficacy of Oral MDM2 Inhibitor RG7388 in the SJSA Human Osteosarcoma Xenograft Model [1]

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Female SJSA tumor-bearing nude mice were orally administered daily doses of RG7388 and blood samples were collected in EDTA tubes from 2 animals/group/time point (1, 2, 4, 8 and 24 hours) after the first (acute PK) or last (chronic PK) dose. Plasma and tumor samples were prepared and analyzed for RG7388 by LC/MS/MS. Mean plasma concentrations were calculated from 2 animals/group/time point. S-9 Efficacy of Oral MDM2 Inhibitor RG7388 in the SJSA Human Osteosarcoma Xenograft Model The anti-tumor efficacy of RG7388 in the SJSA1 model was determined in female nude mice as reported in Tovar et al.1 In the current study, mice were randomized into treatment groups of 10 mice with similar mean tumor volumes of 190-230 mm3 . RG7388 was administered by gavage at doses from 12.5-50 mg/kg daily for two weeks.

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Efficacy of Oral MDM2 Inhibitor RG7388 in the SJSA Human Osteosarcoma Xenograft Model [1]
\The anti-tumor efficacy of RG7388 in the SJSA1 model was determined in female nude mice as reported in Tovar et al.1 In the current study, mice were randomized into treatment groups of 10 mice with similar mean tumor volumes of 190-230 mm3 . RG7388 was administered by gavage at doses from 12.5-50 mg/kg daily for two weeks.

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Pharmacokinetic analysis[2]
\To determine RG7388 plasma concentrations, blood samples were collected from female mice during in vivo antitumor studies. In each treatment group, on the first and/or last dosing day, blood samples (generally n = 2/time point) were collected at various predetermined time points ranging from 0.5 to 24 hours after the last dose. Pharmacokinetic assessment was performed via noncompartmental analysis using Watson v7.4, where parameters were calculated on the basis of the composite concentration–time data from each treatment group and sampling day. Sampling times were reported as nominal time, with concentrations below the limit of quantitation excluded. Parameters reported include plasma half-life (t1/2), Cmax, Tmax, and area under the plasma concentration–time curve from end of dosing to the last bleeding time point (AUC0–24 hours). The AUCs were calculated using the linear trapezoidal rule. The Cmax and Tmax values were taken directly from the plasma concentration–time profiles without extrapolations.

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In vivo activity studies in xenograft tumor models[2]
\Athymic female nude mice (Crl:NU-Foxn1nu) were obtained from Charles River Laboratories. The health of all animals was monitored daily by gross observation and analyses of blood samples of sentinel animals. All animal experiments were performed in accordance with protocols approved by the Institutional Animal Care and Use Committee in our Association for Assessment and Accreditation of Laboratory Animal Care-accredited facility.
At 10 to 12 weeks of age, mice were implanted with a 1:1 mixture of human SJSA osteosarcoma cells (ATCC) suspended in phenol-free Matrigel and PBS. Mice were implanted in the right flank at a concentration of 5 × 106 cells in 0.2 mL total volume. At approximately day 10, animals were randomized according to tumor volume, so that all groups of 10 randomized mice had similar starting mean tumor volumes of 100 to 250 mm3.
Tumor measurements and weights were taken two to three times per week. TGI was calculated from percent change in mean tumor volume compared with the control group. Average percent weight change was used as a surrogate endpoint for tolerability in the experiment. Animals in each group were continuously followed beyond the last day of treatment to see whether tumor regrowth would occur. In this second phase of analysis, survival was calculated using a cutoff individual tumor volume of 1,500 mm3 as a surrogate for mortality. The increase in lifespan (ILS) was calculated as a percentage using the formula: [(median day of death in treated tumor-bearing mice) − (median day of death in control tumor-bearing mice)]/median day of death in control tumor-bearing mice × 100. Statistical analysis was performed as previously described.
RG7388 was administered as an amorphous solid dispersion microbulk precipitate powder containing 30% drug substance and 70% hydroxypropyl methylcellulose acetate succinate polymer that was reconstituted immediately before administration as a suspension in Klucel/Tween, and remaining suspension was discarded after dosing.

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1. For the preclinical scheduling optimization of RG7388, an osteosarcoma xenograft model was established in mice; RG7388 was administered orally at different doses and schedules (30 mg/kg daily, 50 mg/kg twice a week, 50 mg/kg weekly, 10 mg/kg daily), and antitumor activity was evaluated by monitoring tumor growth over time [2]
2. A PKPD model was developed using preclinical data of RG7388 in the mouse osteosarcoma xenograft model; the model was used to investigate the link between RG7388 pharmacokinetics and the time-course of its antitumor effect, and to predict intermittent and continuous dosing regimens for achieving tumor stasis [2]
3. In xenograft models, Idasanutlin (RG7388) was administered orally to evaluate its ability to activate p53, inhibit tumor growth and enhance the survival of model animals [3]

Pharmacokinetics [3] After oral administration of idasanulin, peak plasma concentration is usually reached 6 to 8 hours in a fasting state, and then gradually decreases, with a terminal half-life of about 30 hours (Figure 2A). After the first dose (i.e., day 1) and after repeated dosing (i.e., day 3 of the once-daily × 3 regimen and day 5 of the once-daily × 5 regimen), drug exposure is approximately proportional to dose. However, when the dose exceeds 600 mg, the increase in drug exposure appears to be less than dose-proportional, suggesting that intestinal absorption has reached saturation at this dose level (Figure 2B). However, there are large differences in drug exposure among patients for all dosing regimens (Figure 2B). Compared with the first dose, the drug exposure on the last day of the once-daily × 3 and once-daily × 5 dosing regimens is about twice that of the first dose (Figure 2B), but no drug accumulation was observed in the once-weekly × 3 dosing regimen (data not shown). For a given daily dose, the cumulative idasanutlin exposure was highest with the once-daily (QD) × 5 regimen over the entire 28-day dosing cycle, reflecting a higher total dose (i.e., 5 days of dosing instead of 3 days or 3 single doses).

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Effect of food on idasanutlin pharmacokinetics [3]
Ten patients received 800 mg of idasanutlin, either after a high-fat/high-calorie meal or on an empty stomach. The dosing was performed using a semi-repeated crossover design, resulting in 15 pairs of postprandial and fasting data from the 10 patients. On average, idasanutlin exposure was higher when taken with food (mean maximum plasma concentration was 14% higher, and area under the curve extrapolated to infinity was 43% higher), but the variability was greater and the 90% confidence interval included 1, thus concluding that food had no clinically significant effect on idasanutlin exposure (Online Resource Table S7; Figure 2C).

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Pharmacodynamic Analysis[3]
After idasanutlin administration, the level of circulating macrophage inhibitory cytokine 1 (MIC-1) generally increases in a dose-dependent manner (Figure 2D). Therefore, the trend of MIC-1 response to treatment is consistent with the trend of idasanutlin exposure, as described in the population pharmacokinetic/pharmacodynamic analysis section.
Of the 31 patients treated with idasanutlin, 16 (51.6%) had changes in tumor proliferation assessed by positron emission tomography analysis, and the results showed that during the first treatment cycle, the percentage change in the optimal maximum normalized uptake value (SUVmax) decreased by ≥25% from baseline (online resource figure S2), achieving a partial proliferative response.

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Population Pharmacokinetic/Pharmacodynamic Analysis[3]
Simulations using an indirect PK/MIC-1 model (online resource supplementation method) showed that, despite some variability, MIC-1 release after idasanutlin treatment was concentration-dependent; the higher the idasanutlin concentration, the higher the MIC-1 release. Compared to the daily dosing regimen (same dose), the weekly idasanutlin dosing regimen had a lower maximum release but a more durable effect on MIC-1 over a 28-day treatment period (Figure 3).

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Idasanutlin (RG7388) is an MDM2 (mouse double microsome 2) inhibitor currently under investigation for its anticancer effects, particularly in TP53 wild-type tumors (e.g., acute myeloid leukemia, solid tumors). The following is a pharmacokinetic (PK) overview based on available preclinical and clinical data:
1. Absorption
Route of administration: Oral (tablets).
Bioavailability: Data are limited, but oral absorption is moderate (approximately 30-50% in preclinical models).
Food Effects: High-fat foods may significantly increase absorption (observed in clinical trials). Therefore, it is usually taken with food to improve bioavailability.
2. Distribution
Protein Binding: Highly protein-bound (>99%, primarily bound to albumin).
Volume of Distribution (Vd): Not fully characterized, but likely moderate due to high protein binding.
Tissue Penetration: Preclinical data suggest distribution to tumor tissues, but central nervous system penetration may be limited.
3. Metabolism
Main Pathway: Hepatic metabolism, primarily via CYP3A4 (major) and UGT1A1/UGT1A3 (glucuronidation).
Metabolites: Various oxidative and conjugated metabolites (mostly inactive or weakly active).
Drug Interactions (DDI):
CYP3A4 inducers (e.g., rifampin) → may decrease idasanulin exposure.
CYP3A4 inhibitors (e.g., ketoconazole) → may increase idasanulin exposure.
UGT inhibitors (e.g., atazanavir) → may increase exposure.
4. Elimination
Half-life (t½): Approximately 4–8 hours (significant patient-to-patient variability).
Clearance: Primarily cleared by the liver, with partial excretion via bile.
Excretion: Primarily excreted via feces (approximately 70-80%), with minimal renal excretion (<5%).
5. Pharmacokinetic Variability
Patient-to-patient variability: High, possibly related to differences in CYP3A4/UGT activity, food effects, and protein binding.
Dose-proportionality: Non-linear pharmacokinetics at high doses (absorption or metabolic saturation).
6. Special Populations
Hepatic impairment: Expected to significantly increase exposure (studies are insufficient).
Renal impairment: Unlikely to have a significant impact (minimal renal excretion).
Children/Elderly: Limited data; ongoing research. 7. Clinical Significance
Optimal Dosage: Usually administered once daily or intermittently (e.g., 5 days on/2 days off) to control toxicities (e.g., gastrointestinal reactions, thrombocytopenia).
Therapeutic Drug Monitoring (TDM): TDM can be useful due to the high pharmacokinetic variability.
Idasanulin Pharmacokinetic Summary Table
Parameter Characteristics
Route of Administration: Oral (with food)
Bioavailability: Moderate (~30-50%)
Protein Binding: >99% (albumin)
Metabolism: CYP3A4, UGT1A1/1A3
Half-Life: ~4-8 hours
Excretion: Feces (~70-80%), urine (<5%)
Major Drug Interactions: CYP3A4 inducer/inhibitor
Ongoing Research
Clinical trials continue to refine pharmacokinetic characteristics, especially in combination therapy (e.g., in combination with venetoclax for the treatment of acute myeloid leukemia).

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1. At low doses, the exposure of idasanulin (RG7388) was approximately dose-proportional, but at doses > 600 mg, the dose-proportional relationship was less pronounced; inter-patient exposure variability was high across all dosing regimens [3]
2. Over a 28-day period, the once-daily (QD) × 5 regimen of idasanulin (RG7388) had the highest cumulative exposure [3]

Safety and Tolerability [3] The median duration of treatment for all patients was 36 days (range: 1–726 days), with 15 patients (15.2%) receiving treatment for more than 91 days (Online Resource Table S3). The median (range) of total daily dose for the QW×3, QD×3, and QD×5 groups was 10.5 (2–72), 9.0 (6–42), and 10.0 (1–130), respectively. All 99 patients were included in the safety analysis population; in all cohorts, 78 patients (78.8%) received ≤ 2 treatment cycles. The maximum tolerated dose (MTD) for the once-weekly (QW) × 3-times dosing regimen was 3200 mg (1600 mg twice daily). Dose-limiting toxicities (DLTs) included nausea, thrombocytopenia, and vomiting (see Online Resource Table S4), all of which occurred at or above 1600 mg of total daily dose. The maximum tolerated dose for the once-daily (QD) × 3-dose regimen was 1000 mg (500 mg twice daily). Dose-limiting toxicities included thrombocytopenia, febrile neutropenia, neutropenia, and pancytopenia. The maximum tolerated dose for the once-daily (QD) × 5-dose regimen was 500 mg once daily. Dose-limiting toxicities included thrombocytopenia, neutropenia, febrile neutropenia, and diarrhea. A total of 31 dose-limiting toxicities (DLTs) were reported across all cohorts (n = 99), with ≥1 DLT occurring in 21 patients (21.2%; dose escalation cohort n = 20; apoptosis cohort n = 1). The most common DLT was thrombocytopenia, occurring in 16 of the 99 patients (16.2%). Other DLTs included neutropenia (5 cases [5.1%]), febrile neutropenia (3 cases [3.0%]), nausea (2 cases [2.0%]), and leukopenia, pancytopenia, diarrhea, and vomiting (1 case each [1.0%]). In the dose escalation cohort, the incidence of dose-limiting toxicities (DLTs) was higher with the daily dosing regimen (40% in the QD × 3 group and 32.4% in the QD × 5 group) than with the weekly dosing regimen (8.3%), and the incidence of DLTs related to hematologic and lymphatic disorders was higher with the daily dosing regimen (Online Resource Table S4).
All 99 patients experienced ≥ 1 adverse event (AE) that the investigator considered relevant to the study treatment (Table 1). The most common treatment-related adverse events were diarrhea (74.7%), nausea (71.7%), vomiting (50.5%), decreased appetite (43.4%), and thrombocytopenia (39.4%; online resource table S5). Overall, the QD × 3 regimen had the highest incidence of treatment-related adverse events, while the QD × 5 regimen had the lowest (see online resource table S5). 63 patients (63.6%) experienced ≥ grade 3 adverse events of any cause, with a higher incidence in the QD regimen (see Table 1). The most common ≥ grade 3 adverse events of any cause were thrombocytopenia (29.3%), anemia (20.2%), neutropenia (16.2%), nausea (11.1%), and diarrhea (7.1%). A total of 32 patients (32.3%) reported serious adverse events (SAEs) across all study groups (see Table 1; online resource table S6). Of these, 25 patients (25.3%) reported treatment-related serious adverse events. The most frequently reported disorders (24 of the 25 patients) were related to hematologic and lymphatic disorders: thrombocytopenia/decreased platelet count (14), febrile neutropenia (5), neutropenia/decreased neutrophil count (4), leukopenia/decreased white blood cell count (3), and anemia (2). Treatment-related serious adverse events (SAEs) were more frequently reported with the once-daily (QD) regimen (3 times) and the once-daily (QD) regimen (5 times) compared to the once-weekly (QD) regimen (4 of 36 patients [11.1%]) (QD × 3, 7 of 15 [46.7%]; QD × 5, 13 of 34 [38.2%]) (see online resource table S6).
Most patients (81 of 99 [81.8%]) discontinued treatment for non-safety reasons: disease progression (n = 77), withdrawal of informed consent (n = 3), and other unspecified reasons (n = 1). Eighteen patients (18.2%) withdrew from treatment due to adverse events (AEs), eight of which were considered serious. The rate of discontinuation due to adverse events (AEs) was higher in patients receiving a daily dosing regimen (excluding the apoptosis imaging group) compared to those receiving a once-weekly (QW×3) regimen (20.0% in the QD×3 group, 29.4% in the QD×5 group, and 11.1% in the QD×3 group). The most common adverse events leading to study drug discontinuation in all patients were neutropenia, thrombocytopenia, and pulmonary embolism (all 3.0%). Adverse events associated with study withdrawal were more likely to be hematologic in nature and grade ≥3 in severity. Forty-four patients (44.4%) reported dose adjustments/discontinuations due to adverse events, with similar frequencies for weekly and daily dosing regimens (Table 1). Of these, 16 (44.4%) of the 36 patients receiving a once-weekly (QW) × 3-times dosing regimen required dose adjustments, 7 (46.7%) of the 15 patients receiving a once-daily (QD) × 3-times dosing regimen required dose adjustments, and 18 (52.9%) of the 34 patients receiving a once-daily (QD) × 5-times dosing regimen required dose adjustments. The most common adverse events leading to dose adjustments were thrombocytopenia (24.2%) and neutropenia (9.1%). Overall, seven deaths occurred during treatment or within 28 days of the last dose: five due to disease progression and two due to serious adverse events (SAEs) (Table 1). One death (QW × 3 group) was due to intraperitoneal hemorrhage and pulmonary embolism, both of which were determined to be unrelated to the study treatment. Another death (QD × 5 group) was due to pulmonary embolism, which may be related to the study treatment.

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1. The most common adverse reactions to idasanutlin (RG7388) in patients with advanced malignancies were diarrhea, nausea/vomiting, decreased appetite and thrombocytopenia[3]
2. Dose-limiting toxicities of idasanutlin (RG7388) included nausea/vomiting and myelosuppression; myelosuppression was more common with once-daily dosing and was associated with pharmacokinetic exposure[3]
3. In the first treatment cycle, ≥ grade 3 neutropenia (absolute neutrophil count < 1 × 10⁹ cells/L) and ≥ grade 3 thrombocytopenia (platelet count < 50 × 10⁹ cells/L) were associated with the 28-day cumulative area under the curve (AUC₀-28d) of idasanutlin (RG7388)[3]

[1]. Discovery of RG7388, a potent and selective p53-MDM2 inhibitor in clinical development. J Med Chem. 2013 Jul 25;56(14):5979-83.

[2]. Preclinical optimization of MDM2 antagonist scheduling for cancer treatment by using a model-based approach. Clin Cancer Res. 2014, 20(14), 3742-3752.

[3]. Phase I study of daily and weekly regimens of the orally administered MDM2 antagonist idasanutlin in patients with advanced tumors. Invest New Drugs . 2021 Dec;39(6):1587-1597. https://pubmed.ncbi.nlm.nih.gov/34180037/

Idasanulin has been used in research on tumors, non-Hodgkin's lymphoma, leukemia, myeloid leukemia, acute relapsed plasma cell myeloma, and the treatment of tumors, leukemia, and acute myeloid leukemia. Idasanulin is an orally administered small molecule MDM2 (mouse double microsome 2; MDM2 p53 binding protein homolog) antagonist with potential antitumor activity. Idasanulin binds to MDM2, blocking the interaction between the MDM2 protein and the transcriptional activation domain of the tumor suppressor protein p53. By preventing the MDM2-p53 interaction, p53 is not enzymatically degraded, and its transcriptional activity is restored. This may lead to p53-mediated apoptosis in tumor cells. MDM2 is a zinc finger nucleophosphorus protein and a negative regulator of the p53 pathway; it is often overexpressed in cancer cells and is closely related to cancer cell proliferation and survival.

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Drug Indications
Treatment of all malignant tumors (excluding tumors of the nervous system, hematopoietic and lymphoid tissues)
Treatment of acute lymphoblastic leukemia, treatment of acute myeloid leukemia

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Restoring p53 activity by inhibiting p53-MDM2 interaction is considered an attractive cancer treatment approach. However, the hydrophobic protein-protein interaction surface presents a significant challenge to the development of small molecule inhibitors with ideal pharmacological properties. RG7112 is the first small molecule p53-MDM2 inhibitor to enter clinical development. This article reports the discovery and characterization of the second-generation clinical MDM2 inhibitor RG7388, which has higher potency and selectivity. [1]

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Objective: The MDM2 antagonist RG7112 has been shown to have antitumor clinical activity, but patients have poor tolerance to daily dosing. This article explores the feasibility of an intermittent dosing regimen using the second-generation nutritional inhibitor RG7388 (which has higher selectivity and potency) to guide the selection of the initial dosing regimen in a phase I clinical trial. Experimental Design: Based on preclinical data, we established a pharmacokinetic-pharmacodynamic (PKPD) model to determine alternative dosing regimens required to induce optimal antitumor activity with RG7388. This PKPD model was used to investigate the pharmacokinetics of RG7388 and the time progression of its antitumor effect in a mouse osteosarcoma xenograft model. These data were used to prospectively predict intermittent and continuous dosing regimens to achieve tumor suppression in the same model system. Results: RG7388-induced apoptosis was delayed relative to drug exposure time, without the need for continuous treatment. In preliminary efficacy testing, RG7388 dosing regimens of 30 mg/kg daily and 50 mg/kg twice weekly were statistically equivalent in our tumor model. Furthermore, the weekly 50 mg/kg dosing regimen was comparable in efficacy to the daily 10 mg/kg dosing regimen. Based on these data, modeling and simulations proposed several possible intermittent clinical dosing regimens. Further preclinical analyses confirmed the feasibility of these regimens. Conclusion: In addition to long-term dosing, intermittent dosing regimens of RG7388 can also achieve antitumor activity, as predicted by modeling and simulations. These alternatives may help improve the tolerability of long-term RG7388 administration and provide clinical benefits. Therefore, the clinical trials of RG7388 selected two dosing regimens: once weekly (qw) and once daily for five consecutive days (5 days of treatment/23 days of withdrawal, qd). [2]

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Objective: The oral MDM2 antagonist idasanutlin inhibits p53-MDM2 interaction, thereby activating p53, inhibiting tumor growth, and improving survival in xenograft models. Methods: We conducted a phase I study of idasanutlin (microprecipitated bulk powder formulation) to determine its maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, food effects, and clinical activity in patients with advanced malignancies. The dosing regimens included once weekly for 3 weeks (QW × 3), once daily for 3 consecutive days (QD × 3), or once every 28 days for 5 consecutive days (QD × 5). We also analyzed p53 activation and the antiproliferative effect of idasanutlin. Results: A total of 85 patients were enrolled in the dose escalation phase (once weekly for 3 weeks, n = 36; once daily for 3 weeks, n = 15; once daily for 5 weeks, n = 34). The maximum tolerated daily dose (MTD) was: 3200 mg once weekly for 3 weeks; 1000 mg once daily for 3 weeks; and 500 mg once daily for 5 weeks. The most common adverse events were diarrhea, nausea/vomiting, decreased appetite, and thrombocytopenia. Dose-limiting toxicities were nausea/vomiting and myelosuppression; the incidence of myelosuppression was higher with the once-daily dosing regimen and was correlated with pharmacokinetic exposure. At low doses, idasanutlin exposure was approximately dose-proportional, but at doses >600 mg, exposure was not dose-proportional. Although there were significant inter-patient differences in exposure across all dosing regimens, the once-daily, five-dose regimen resulted in the highest cumulative idasanutlin exposure over the entire 28-day period. No significant effect of food on pharmacokinetic exposure was observed. MIC-1 levels were higher with the once-daily regimen, and this increase was dose-dependent. Optimal efficacy was achieved with disease stabilization in 30.6% of patients, including two sarcoma patients whose disease stabilization lasted over 600 days. Conclusion: Idasanutlin exhibits dose- and regimen-dependent p53 activation and achieves durable disease stabilization in some patients. Based on these findings, the once-daily, five-dose regimen was selected for further development. [3]

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1. RG7388 is the second-generation clinical MDM2 inhibitor following RG7112 (the first small molecule p53-MDM2 inhibitor in clinical development), with better efficacy and selectivity[1]
2. Restoring p53 activity by inhibiting p53-MDM2 interaction is a promising cancer treatment strategy, but the hydrophobicity of the p53-MDM2 protein-protein interaction surface poses a major challenge to the development of small molecule inhibitors with good pharmacological properties[1]
3. Preclinical data of RG7388 were modeled and simulated to identify several potential intermittent clinical dosing regimens, which were validated through further preclinical studies; finally, the regimen of once a week (qw) and once a day for five consecutive days (5 days of treatment/23 days of withdrawal, qd) was selected for the clinical trial of RG7388[2]
4. In the Phase I study, Idasanutlin (RG7388) It was formulated as a microprecipitate powder for oral administration; the maximum tolerated dose (MTD) was: 3200 mg once a week (QW) × 3 times, 1000 mg once a day (QD) × 3 times, and 500 mg once a day (QD) × 5 times [3]
5. In the Phase I study of Idasanutlin (RG7388), 30.6% of patients with advanced tumors had stable disease, including 2 patients with sarcoma whose disease stability lasted for more than 600 days; therefore, the QD × 5 regimen was selected for further clinical development [3]
6. The Phase I study of Idasanutlin (RG7388) was registered on ClinicalTrials.gov on October 31, 2011 (registration number: NCT01462175) [3]

C31H29CL2F2N3O4

616.48

615.15

C, 60.40; H, 4.74; Cl, 11.50; F, 6.16; N, 6.82; O, 10.38

1229705-06-9

Idasanutlin-d3-1;Idasanutlin (enantiomer)

53358942

White to off-white solid powder

1.4±0.1 g/cm3

737.3±60.0 °C at 760 mmHg

399.7±32.9 °C

0.0±2.5 mmHg at 25°C

1.623

7.09

3

8

8

42

1040

4

ClC1=C([H])C([H])=C([H])C(=C1F)[C@@]1([H])[C@]([H])(C(N([H])C2C([H])=C([H])C(C(=O)O[H])=C([H])C=2OC([H])([H])[H])=O)N([H])[C@@]([H])(C([H])([H])C(C([H])([H])[H])(C([H])([H])[H])C([H])([H])[H])[C@]1(C#N)C1C([H])=C([H])C(=C([H])C=1F)Cl

TVTXCJFHQKSQQM-LJQIRTBHSA-N

InChI=1S/C31H29Cl2F2N3O4/c1-30(2,3)14-24-31(15-36,19-10-9-17(32)13-21(19)34)25(18-6-5-7-20(33)26(18)35)27(38-24)28(39)37-22-11-8-16(29(40)41)12-23(22)42-4/h5-13,24-25,27,38H,14H2,1-4H3,(H,37,39)(H,40,41)/t24-,25-,27+,31-/m0/s1

4-[[(2R,3S,4R,5S)-3-(3-chloro-2-fluorophenyl)-4-(4-chloro-2-fluorophenyl)-4-cyano-5-(2,2-dimethylpropyl)pyrrolidine-2-carbonyl]amino]-3-methoxybenzoic acid

Idasanutlin; RG-7388; RO-5503781; RG 7388; RO5503781; 1229705-06-9; RG7388; RG-7388; Idasanutlin (RG-7388); Idasanutlin (RG7388); RO5503781; 4-((2R,3S,4R,5S)-3-(3-chloro-2-fluorophenyl)-4-(4-chloro-2-fluorophenyl)-4-cyano-5-neopentylpyrrolidine-2-carboxamido)-3-methoxybenzoic acid; RG7388; RO 5503781

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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 (4.06 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 2: 5% DMSO+40% PEG 300+5% Tween 80+ddH2O: 1.25mg/mL

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Solubility in Formulation 3: 10 mg/mL (16.22 mM) in 0.5%HPMC 1%Tween80 (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.

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