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The ability to predict human liver-to-plasma unbound partition coefficient (Kpuu) is important to estimate unbound liver concentration for drugs that are substrates of hepatic organic anion-transporting peptide (OATP) transporters with asymmetric distribution into the liver relative to plasma. Herein, we explored the utility of PXB chimeric mice with humanized liver that are highly repopulated with human hepatocytes to predict human hepatic disposition of OATP substrates, including rosuvastatin, pravastatin, pitavastatin, valsartan, and repaglinide. In vitro total uptake clearance and transporter-mediated active uptake clearance in C57 mouse hepatocytes were greater than in PXB chimeric mouse hepatocytes for rosuvastatin, pravastatin, pitavastatin, and valsartan. Consistent with in vitro uptake data, enhanced hepatic uptake and resulting total systemic clearance were observed with the above four compounds in severely compromised immune-deficient (SCID) control mice compared with the PXB chimeric mice, which suggest that mouse has a stronger transporter-mediated hepatic uptake than human. In vivo liver-to-plasma Kpuu from PXB chimeric and SCID control mice were also compared, and rosuvastatin and pravastatin Kpuu in SCID mice were more than 10-fold higher than that in PXB chimeric mice, whereas pitavastatin, valsartan, and repaglinide Kpuu in SCID mice were comparable with Kpuu in PXB chimeric mice. Finally, PXB chimeric mouse liver-to-plasma Kpuu values were compared with the reported human Kpuu, and a good correlation was observed as the PXB Kpuu vales were within 3-fold of human Kpuu Our results indicate that PXB mice could be a useful tool to delineate hepatic uptake and enable prediction of human liver-to-plasma Kpuu of hepatic uptake transporter substrates. SIGNIFICANCE STATEMENT: We evaluated PXB mouse with humanized liver for its ability to predict human liver disposition of five organic anion-transporting polypeptide transporter substrates. Both in vitro and in vivo data suggest that mouse liver has a stronger transporter-mediated hepatic uptake than the humanized liver in PXB mouse. More importantly, PXB liver-to-plasma unbound partition coefficient (Kpuu) values were compared with the reported human Kpuu, and a good correlation was observed. PXB mice could be a useful tool to project human liver-to-plasma Kpuu of hepatic uptake transporter substrates.

Background: CDK12 has emerged as an attractive cancer target due to its role in transcription and DNA damage repair regulation. In pre-clinical models, small molecule CDK12 inhibitors have demonstrated promising tumor killing effect, especially in combination with DNA damaging agents. Here we profiled new oral and selective CDK12 inhibitors. Material and methods: ADP-glo࣪ assays: inhibition of recombinant CDK12/CyclinK, CDK2/CyclinE, CDK7/CyclinH/MAT1 and CDK9/CyclinT2 was measured by assessing ADP converted from ATP via luminescent signal at Km and 20x Km ATP. Kinome screen: 1 µM of Compound A was tested in duplicate against 370 kinases at 10 µM ATP in the radiometric HotSpot™ assay. Cellular assays: p-Ser2, p-Ser5 and total RNA pol II signals were assessed 4hrs after compound treatment while ɣH2AX and BRCA1 signals were measured after 24-48hr compound treatment via Immunofluorescence (IF) assays. Cell proliferation was determined using cell titer glo after 48-72hrs compound treatment. Apoptosis was measured by annexin V/PI staining and flow cytometry analysis after 48-72hrs of treatment. Cell cycle profile was evaluated with Click-iT-EdU and FxCycle violet stain and flow cytometry analysis following 24-48hrs of treatment. Mouse xenograft: balb/c mice were implanted subcutaneously with H1048 or MDA-MB-468 cells and randomized for treatment with test drug or vehicle when tumors reached 150-200mm3. Mice were dosed BID through oral administration for 4 weeks. Combination effect of Compound A and lurbinectedin was tested in vivo. Lurbinectedin and Compound A were dosed QW and BID respectively for 28 days in H1048 CDX model. Results: A series of CDK12 inhibitors were designed and profiled in biochemical and cellular assays. A representative member of the class, Compound A, exhibited selectivity over CDK2, CDK7, and CDK9 of 46-, 27-, and 9-fold, respectively. Compound A inhibited proliferation in a panel of cell lines with EC50 in the low nanomolar range. Compound A treatment led to dose dependent apoptosis in multiple cancer cell lines and induced G2/M arrest in cancer cell lines. In vitro, combination treatment with Compound A and lurbinectedin lead to increased DNA damage accumulation, decreased homologous recombination repair, and overall enhanced antiproliferation. Dose dependent tumor growth inhibition in SCLC and TNBC CDX models was observed with Compound A treatment. Enhanced and durable antitumor effect was observed with lurbinectedin and Compound A combination compared to single agent treatment in vivo. Conclusions: We designed and profiled orally available, CDK12 selective inhibitors with potent activity as single agent in vitro and in vivo in multiple cancer models. Compound A demonstrated enhanced antitumor effect in vitro and in vivo when combined with DNA damaging agents. These data support the rationale for advancing one or more members of this class toward clinical development. Citation Format: Shan hu, David Moebius, Wojciech Dworakowski, Elliott Cooper, Derek LaPlaca, Sydney Alnemy, Phone Perera, Jason Marineau, Claudio Chuaqui, John P. Carulli, Eric Olson. An oral and selective CDK12 inhibitor demonstrates robust anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5393.

In Drug Discovery, pharmacology studies often require benign formulation compositions for safe administration in animal models. Here, we applied Adaptive Focused Acoustics™ (AFA) to a molecular scaffold with challenging physicochemical properties for intraperitoneal administration. Nanosuspensions can be prepared at small scales and provide broad applicability. Our results show that nanosuspension formulations prepared by AFA have improved PK performance relative to a DMSO solution formulation that is prone to precipitation in-vivo.

The lipid kinase phosphoinositide 3-kinase γ (PI3Kγ) has attracted attention as a potential target to treat a variety of autoimmune disorders, including multiple sclerosis, due to its role in immune modulation and microglial activation. By minimizing the number of hydrogen bond donors while targeting a previously uncovered selectivity pocket adjacent to the ATP binding site of PI3Kγ, we discovered a series of azaisoindolinones as selective, brain penetrant inhibitors of PI3Kγ. This ultimately led to the discovery of 16, an orally bioavailable compound that showed efficacy in murine experimental autoimmune encephalomyelitis (EAE), a preclinical model of multiple sclerosis.

Introduction: CDK7 is a key regulator of transcription and cell cycle progression and has been implicated in multiple tumor types driven by aberrant transcriptional (e.g., MYC-, ESR1-activation) and/or aberrant cell cycle control (e.g., loss of RB pathway checkpoint function) mechanisms. SY-5609 is a potent and selective CDK7 inhibitor currently in development in patients with solid tumors (NCT04247126). To assess the potential for SY-5609 development in heme malignancies, we evaluated SY-5609 activity in preclinical models of mantle cell lymphoma (MCL). MCL is an aggressive B cell lymphoma driven by genetic alterations in RB pathway genes (e.g. CCND1, RB1, CDKN2A) and by hyper-activation of B-cell receptor (BCR) signaling leading to activation of NF-kB-dependent transcriptional programs that drive cell proliferation and survival. Our results support evaluation of SY-5609 in MCL patients and highlight the potential for combining SY-5609 with Bruton's Tyrosine Kinase (BTK) inhibitors, inhibitors of BCR signal transduction approved for treatment of MCL. Methods: SY-5609 in vitro antiproliferative activity was assessed in a panel of 7 MCL cell lines by evaluating growth rate inhibition (GR) curve metrics GR 50 (drug concentration at which growth rate is inhibited by 50%) and GR max (maximum depth of response) after 5-days of treatment. SY-5609 pharmacodynamic (PD) responses and combination activity with the BTK inhibitor acalabrutinib were further assessed in MCL cell line Mino-1. PD activity was assessed by measuring transcriptional changes in POLR2A using a NanoString-based PD assay from the SY-5609 solid tumor trial. Combination activity in vitro was assessed by comparing GR curve metrics between acalabrutinib, SY-5609, and acalabrutinib in combination with SY-5609. Expression of CCND1 and E2F1, a key transcriptional regulator of DNA replication commitment and progression, were assayed via western blot. Combination activity in vivo was assessed in mice bearing Mino-1 xenograft tumors by comparing tumor growth rate inhibition (GRI) and body weight change in mice treated with acalabrutinib (15mg/kg, QD) and/or SY-5609 (0.5mg/kg, BID, days 1-7 and 15-21) over 25 days. Results: SY-5609, as a single agent, potently inhibited proliferation of all 7 MCL cell lines tested with a GR 50 geometric-mean of 7 nM (range: 2 to 20 nM) and a GR max geometric-mean of -0.2 (range: -0.6 to 0.2). In MCL cell line Mino-1, SY-5609 induced a dose-dependent increase in POLR2A expression to levels associated with SY-5609 antiproliferative activity in Mino-1 cells in vitro and to levels comparable with those observed in peripheral blood mononuclear cells (PBMCs) collected from SY-5609 solid tumor trial patients. In combination with acalabrutinib, SY-5609 demonstrated synergistic antiproliferative activity in Mino-1 cells in vitro, a dose-dependent decrease in acalabrutinib GR 50 (up to ~2-fold at the highest SY-5609 concentration tested, 5nM), and a dose-dependent increase in GR max (up to ~10-fold). In addition, the combination of SY-5609 and acalabrutinib caused dose-dependent decreases in CCND1 and E2F1 protein expression in vitro, which were not observed with either single agent alone. Finally, in mice bearing Mino-1 xenografts, the combination of SY-5609 and acalabrutinib significantly (p < 0.01) increased tumor GRI relative to each single agent at the doses and regimens tested and was well tolerated (no difference in body weight changes relative to vehicle treated mice). Conclusions: SY-5609 is a potent and selective CDK7 inhibitor that demonstrates antiproliferative activity in MCL cells in vitro, associated with PD changes comparable to those observed in patients enrolled in the SY-5609 solid tumor trial (ENA, 2020). The combination of SY-5609 and acalabrutinib is synergistic in MCL cells in vitro and inhibits expression of key cell cycle regulatory proteins CCND1 and E2F1 at concentrations that are preclinically subtherapeutic for either single agent alone. The combination of SY-5609 and acalabrutinib is also significantly more effective at inhibiting MCL xenograft growth in vivo than either single agent. These results support evaluation of SY-5609, including in combination with BTK inhibitors, in patients with mantle cell lymphoma. Disclosures Johannessen: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Henry: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Sawant: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. D'Ippolito: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Ke: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Lefkowitz: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Eaton: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Dworakowski: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Rosario: Syros Pharmaceuticals: Current Employment. Hodgson: Syros Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company.

3585 Background: Colorectal cancer (CRC) is driven by genetic alterations that result in constitutive activation of oncogenic transcription factors (eg β-catenin, MYC) and of mitogenic signaling and cell cycle progression (driven by oncogenic mutations in KRAS and BRAF). CDK7 is a key regulator of transcription, through phosphorylation of the CTD domain of RNA Polymerase II, and of cell cycle progression, through phosphorylation of the cell cycle kinases CDK1, 2, 4, and 6. This dual role of CDK7 suggests inhibitors of CDK7 may be effective in the treatment of CRC. SY-5609 is an oral, noncovalent, potent and highly selective CDK7 inhibitor in phase 1 clinical development for patients with advanced solid tumors including CRC (NCT04247126). Here we report on the activity of SY-5609 in patient-derived xenograft (PDX) models of CRC. Methods: SY-5609 was administered once daily (QD) by oral gavage for 21 days (end of treatment, EOT) to mice bearing PDX models of CRC. The relationship between SY-5609 dose, pharmacodynamic (PD) changes in xenograft tissue, tumor growth inhibition (TGI), and mouse body weight (BW) was evaluated across a range of doses. SY-5609 TGI activity was also evaluated at sub-maximum-tolerated-dose levels across a panel of 30 independent CRC models including BRAF-, KRAS-, and non-BRAF/KRAS-mutant (wild type) models (n = 10 per group). Results: SY-5609 induced dose-dependent TGI in BRAF-mutant CRC PDX tumors, with tumor regressions observed at well tolerated doses (no BW loss at EOT), and no tumor regrowth for 2+ weeks after treatment was discontinued. Dose-dependent TGI was associated with dose-dependent PD changes in PDX tumor tissue. Across 30 PDX models, SY-5609 at well-tolerated doses (average BW loss of 0% at EOT across all models) induced ≥50% TGI in 67% (20/30) of models. Deep responses (≥90% TGI or regressions) were observed in 23% (7/30) of models, with enrichment for deep responses in BRAF mutant models (50%, 5/10) relative to KRAS mutant (10%, 1/10), and wild type (10%, 1/10) models. Conclusions: Daily oral dosing of the CDK7 inhibitor SY-5609 induces robust TGI, including regressions, in CRC PDX models at well-tolerated doses. Dose-dependent TGI is associated with dose-dependent PD changes in CRC PDX tumor tissue. These results highlight the therapeutic potential of SY-5609 in CRC and support the evaluation of SY-5609 in CRC patients in early phase clinical trials. SY-5609 is in phase 1 clinical development for patients with advanced solid tumors including CRC (NCT04247126).

This article describes the discovery and characterization of nanocolloidal structures formed between VX-985 (an orally administered inhibitor of hepatitis C virus protease) and the bile salt, sodium taurocholate at concentrations of the latter >4 mM. These complexes (1) distribute narrowly in size around a mean diameter of 260 nm, (2) separate from solution only with ultracentrifugation, and (3) appear to influence the absorption of VX-985 from the intestinal tract in vivo, in rodents and humans. Although the oral bioavailability of suspensions of its solid forms is poor, addition of vitamin E D-alpha-tocopherol polyethylene glycol 1000 succinate to dosing vehicles improves the fraction absorbed of the compound in vivo. In vitro characterization is compatible with the hypothesis that surfactants like D-alpha-tocopherol polyethylene glycol 1000 succinate preclude nanocolloidal structures and increase the bioavailability by increasing the rate of absorption of VX-985. This study, while specific to VX-985, provides a route to circumvent the poor oral bioavailability caused by formation of kinetically stable complexes between bile salts and drug molecules. This study also underscores the importance of characterizing aggregation phenomenon that may be observed in solubility measurements during preclinical formulation development.

Rat liver, as well as other species, contains numerous sex-dependent isoforms of cytochrome P450 (P450) that are regulated by the sexually dimorphic profiles of circulating growth hormone. During puberty, young adulthood, and senescence, changes in the hormonal profiles appear to be responsible for alterations in age-associated expression levels of selective P450 isoforms. In contrast, little is known about the growth hormone secretory profiles and their P450-dependent expression levels during middle age. In the present study, we observed subtle changes in the hormonal concentrations, and frequencies of peaks and interpulse periods in the sexually dimorphic growth hormone profiles of 1-year-old male and female rats correlated to suppression of male-specific isoforms CYP2C11 and CYP2C13 and female-predominant CYP2C7. To identify possible causes for the age-associated changes in the circulating growth hormone profiles, the responsiveness of the hypothalamic-pituitary axis to growth hormone secretagogues clonidine and growth hormone-releasing factor (GRF) were examined in middle-aged male and female rats. In spite of the same sexually dimorphic response in young adult and middle-aged rats to both secretogogues (males > females), the pituitary somatotrophs in the older animals exhibited a dramatic decrease in sensitivity to clonidine, characterized by subnormal growth hormone release levels and an inordinate delay in pituitary response to clonidine stimulation. Results from similar studies conducted on middle-aged arcuate nucleus-lesioned rats suggest that a decline in GRF secretion is a possible contributor to the age-associated alterations in plasma growth hormone profiles during middle age. These changes in GRF-induced, sexually dimorphic secretory growth hormone profiles and the accompanying decline in P450 expression levels may anticipate similar, but more profound, changes to occur during senescence.

The importance of photoperiod and ambient temperature on the accumulation of cadmium in the liver and kidneys of bank voles was determined in the present study. Males and females, aged 1 month, were given 3.0 micrograms Cd ml-1 drinking water and divided into four groups according to photoperiod (16 h light/8 h dark and 8 h light/16 h dark) and ambient temperature (20 or 5 degrees C); liver and kidneys were removed for cadmium as well as copper, iron and zinc analyses at the end of 6 weeks. Bank voles exposed to 5 degrees C in both photoperiods consumed approximately 30% less water containing cadmium than those kept at 20 degrees C. However, the total accumulation of cadmium in the liver and kidneys of males and females exposed to the low temperatures was 4.3-4.8 and 2.2-3.3 times less than that in animals maintained at room temperature in the long and short photoperiod, respectively. Simultaneously, the low temperature brought about an increase in the copper concentrations in the liver (12-43%) and kidneys (47-78%), giving rise to an inverse correlation between the cadmium accumulation and the tissue copper concentration. In contrast to cadmium and copper, the concentrations of iron and zinc were affected primarily by photoperiod. These findings indicate that ambient temperature is an important determinant of cadmium retention in the bank vole. It appears that low temperature decreases tissue cadmium accumulation not only by reducing cadmium intake but also through changes in copper metabolism.

Immune checkpoint inhibitors have generated impressive clinical responses, however, a number of patients and cancer types remain resistant to checkpoint blockade. Immunosuppressive cells such as Tregs and MDSCs in the tumor microenvironment are hypothesized to mediate this resistance. The gamma (γ) isoform of PI3K has long been known to modulate myeloid and lymphocyte cell migration and function, including trafficking of monocytic and granulocytic cells into inflamed tissues such as tumors. Here we report the identification and characterization of BVD-723, a PI3Kγ selective small molecule kinase inhibitor which demonstrated single agent and enhanced combination anti-tumor activity[xx]with either an anti-PD-1 or anti-CTLA-4 antibody. In a mouse syngeneic colon cancer model,[xx]BVD-723 in combination with anti-PD-1 or anti-CTLA-4 resulted in complete regression[xx]of tumors in 35% (7/20) and 60% (12/20) of animals treated with each antibody respectively [versus 0% (0/20) and 5% (1/20) with either antibody alone]. Interestingly, the anti-tumor activity was coupled with a decrease in tumor infiltrating Tregs, granulocytic MDSCs, CD4+ T cells and an increase in the CD8+/Treg ratio, suggesting that inhibition of PI3Kγ by BVD-723 promotes immune-reactivation in the tumor microenvironment. Additionally, BVD-723 demonstrated potent synergy with an anti-PD-1 antibody in a syngeneic mouse model of lymphoma. Single agent BVD-723 activity was also observed in syngeneic mouse models of pancreas, colon, lymphoma and bladder cancers. Results from completed safety pharmacology, toxicology and in vivo efficacy studies support clinical evaluation of BVD-723[xx]as a monotherapy or in combination with the checkpoint inhibitors in cancer.[xx] Citation Format: Saurabh Saha, Linping Zhang, Thomas Hoock, Alex Aronov, Sudipta Mahajan, Michael Boyd, Jon Come, Veronique Damagnez, Wojciech Dworakowski, Suvarna Khare-Pandit, Arnaud LeTiran, Cameron Moody, Harwin O'Dowd, Joseph Prezioso, Setu Roday, Xiaoyan M. Zhang. A novel PI3K gamma isoform selective small molecule kinase inhibitor demonstrates single agent anti-tumor activity and enhanced combination activity with checkpoint blockade in syngeneic mouse models of cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-B15.

Adult male and female rat hepatocytes were individually transplanted into the spleens of adult male and female rats. The recipients were euthanized at either eight, sixteen, thirty, or forty-five weeks following transplantation, at which time hepatic and splenic levels of liver-specific rat albumin mRNA as well as sex-dependent transcript levels of CYP2C11, -2C12, -2C7, -2A1, and -3A2—which accounts for > 60% of the total concentration of hepatic constituent cytochrome P450—were determined. Whereas the pre-infused hepatocytes expressed their expected cytochrome P450 sexual dimorphisms (female-specific CYP2C12, male-specific CYP3A2, and female-predominant CYP2A1), their post-transplantational competence now reflected the sexual dimorphisms of the recipient (as observed in the host’s liver), which supports the concept that the sex-dependent growth hormone circulating profiles are the determinants regulating the expression levels of hepatic cytochrome P450. Also expressed at normal concentrations in the pre-infused hepatocytes, male-specific CYP2C11 and female-predominant CYP2C7 were inexplicably undetectable in the spleens of both recipient males and females, regardless of the sex of the donor hepatocytes, almost one year after transplantation.

Although in vivo expression levels of the male-specific hepatic isoforms of cytochrome P450 (P450) (CYP2C11, CYP2C13, CYP2A2, and CYP3A2) are determined by the episodic growth hormone profile secreted by male rats, these isoforms have been completely refractory to growth hormone regulation in hepatocyte culture. By using species-specific rat growth hormone, at subphysiologic in vivo concentrations administered in two daily episodic pulses, we successfully induced CYP2C11 and CYP2A2 to near normal concentrations. Whereas inductive levels of CYP2C13 were subnormal, CYP3A2 was unresponsive to all hormonal treatments, quickly declining to undetectable concentrations. In agreement with in vivo findings, we observed that induction levels of the isoforms were always greatest when the male hepatocytes were exposed to the masculine-like episodic growth hormone profile and least stimulated by the continuous feminine-like hormone profile. When administered alone, dexamethasone consistently increased isoform levels. However, when administered with growth hormone, the glucocorticoid was always antagonistic, suppressing growth hormone induction of CYP2C11, CYP2C13, and CYP2A2. Finally, the P450 isoforms were completely unresponsive to all treatments when the hepatocytes were derived from female rats, supporting earlier findings that expression levels of sexually dimorphic P450 isoforms are inherently irreversible between sexes.

Sex differences in drug metabolism have been reported in numerous species, including humans. In rats and mice, sex-dependent differences in circulating growth hormone profiles are responsible for the differential expression of multiple sex-dependent isoforms of cytochrome P450, which is the basis for the sexual dimorphism in drug metabolism. In contrast, very little is known about sex differences in human isoforms of cytochrome P450 and their regulation by growth hormone. In this study, we have examined the effects of physiologic-like exposure doses to dexamethasone and/or pulsatile (masculine) or constant (feminine) human growth hormone on expression levels of CYP3A4, 1A2, 2D6, and 2E1 and the glucocorticoid and growth hormone receptors in hepatocyte cultures obtained from men and women donors. We report that growth hormone can regulate expression of CYP3A4, 1A2, and 2D6. The masculine-like pulsatile growth hormone profile suppresses dexamethasone-induced CYP3A4, 1A2, and 2D6, whereas the feminine-like constant profile is permissive allowing isoform expression to be equal to or greater than glucocorticoid induction alone. There are intrinsic sexual differences in hepatocytes of men and women resulting in different levels of responsiveness of CYP3A4, 1A2, and hormone receptor expression to the same sexually dimorphic growth hormone profiles. Last, although real, the sexually dimorphic effects of growth hormone on human cytochrome P450 expression are not as dramatic as those observed in rats and could easily be overlooked by the heterogeneous backgrounds of human populations.