Small Molecule Hedgehog Research Articles

681 Development of a topical Hedgehog inhibitor for prevention of new surgically eligible basal cell carcinomas in patients with Gorlin Syndrome: Phase 3 trial

Identification of PTCH1 gene mutations in the Gorlin syndrome two decades ago led to the development of small molecule Hedgehog (HH) inhibitors that replace the function of the mutant gene. These drugs have remarkable oral efficacy against advanced BCCs and off-label vs. the multiple BCCs in patients with Gorlin syndrome. Unfortunately, on target, extra-cutaneous adverse effects cause patients to stop these drugs, after which BCCs in complete clinical and histologic remission generally recur. Therefore, PellePharm is developing a small molecule HH inhibitor for topical use. Our goal is to develop a drug that produces skin concentrations high enough to inhibit HH signaling but not so high that circulating levels produce the unwanted adverse effects. We have incorporated the cyclopamine derivative patidegib into a gel that in two Phase 2 trials has demonstrated efficacy potential vs. BCCs - complete response (12 of 45 tumors in patidegib topical gel arms vs. 0 of 16 in vehicle) and fewer new BCCs (3 out of 12 subjects in patidegib topical gel arms vs. 3 out of 5 in vehicle; ITT one-sided P=0.05); with none of the significant oral HH inhibitor class adverse events observed. Very low to undetectable systemic exposure of the drug has been observed - circulating levels 500-1000x lower than those when patidegib is administered orally. These data suggest that the benefit-risk of patidegib topical gel in patients with Gorlin syndrome is positive. Therefore, we have initiated a Phase 3 Trial in North America and Europe with the aim of enrolling 150 Gorlin subjects randomized 1:1 for application of active vs. placebo gel to the face for a year, testing prevention of the development of new surgically eligible BCCs (ClinicalTrials.gov Identifier: NCT03703310). Patients interested in participating and clinicians interested in more details can contact us at [email protected]

A small molecule Hedgehog agonist HhAg1.5 mediated reprogramming breaks the quiescence of noninjured liver stem cells for rescuing liver failure

Liver is the second most transplanted organ according to United network for organ sharing. Due to shortage of compatible donors, surgical difficulties, immunological hindrance, and high postoperative cost, stem cell therapy is an attractive substitute of liver transplant for millions of patients suffering from hepatic failure. Due to several technical limitations such as viral integration, inefficient differentiation, and adult phenotypes and epigenetic memory of fibroblasts, induced pluripotent stem cells, mesenchymal stem cells, or induced hepatocyte may not present a great clinical substitute for liver transplant. We pioneered a novel technology for robust expansion of quiescent liver stem cells (LSCs) from mice via utilizing of Hedgehog agonist HhAg1.5 for 3 weeks. These expanded LSCs retained stem-like properties after multiple passaging and differentiated to hepatocytes and cholangiocytes. Grafting of ex vivo expanded LSCs in Fah-/- Rag2-/-Il2rg-/- knockout mice, significantly increased life span compared to control group (P < 0.001). Thus in this study, we provide a promising viable substitute for primary hepatocytes for regenerative medicine and for life-threatening metabolic liver diseases.

L-Carnitine Reduces Muscle Cramps in Patients taking Vismodegib

Vismodegib is an oral, small-molecule hedgehog pathway inhibitor (HHI) approved for the treatment of locally advanced and metastatic basal cell carcinoma. While an effective treatment option for these conditions, HHI therapy is associated with muscle cramps in a significant number of patients. This adverse effect negatively impacts patient quality of life and patient adherence to the prescribed treatment regimen.Levocarnitine (L-carnitine) is a trimethylated amino acid known to play a critical role in lipid metabolism. It has antioxidant properties, and several studies have illustrated its effectiveness in lessening the severity of muscle cramps in various disease processes.We present three patients who developed muscle cramping associated with vismodegib treatment for basal cell carcinoma. Each was started on L-carnitine therapy, and all three reported a significant decrease in the severity of their muscle cramps to the point that they were able to continue HHI therapy without taking a drug holiday. These cases illustrate a promising treatment option for the most common side effect associated with HHI treatment.

A Novel and Efficient Route for Synthesis of Taladegib

Taladegib (LY-2940680), a small molecule Hedgehog signalling pathway inhibitor, was obtained from N-benzyl-4-piperidone via Borch reductive amination, acylation with 4-fluoro-2-(trifluoromethyl)benzoyl chloride, debenzylation, substitution with 1,4-dichlorophthalazine and Suzuki cross-coupling reaction with 1-methyl-1H-pyrazole-5-boronic acid. The advantages of this synthesis route were the elimination of Boc protection and deprotection and the inexpensive starting materials. Furthermore, the debenzylation reaction was achieved with simplified operational procedure using ammonium formate as hydrogen source that provided high reaction yield. This synthetic procedure was suitable for large-scale production of the compound for biological evaluation and further study.

Control of inflammation by stromal Hedgehog pathway activation restrains colitis

Inflammation disrupts tissue architecture and function, thereby contributing to the pathogenesis of diverse diseases; the signals that promote or restrict tissue inflammation thus represent potential targets for therapeutic intervention. Here, we report that genetic or pharmacologic Hedgehog pathway inhibition intensifies colon inflammation (colitis) in mice. Conversely, genetic augmentation of Hedgehog response and systemic small-molecule Hedgehog pathway activation potently ameliorate colitis and restrain initiation and progression of colitis-induced adenocarcinoma. Within the colon, the Hedgehog protein signal does not act directly on the epithelium itself, but on underlying stromal cells to induce expression of IL-10, an immune-modulatory cytokine long known to suppress inflammatory intestinal damage. IL-10 function is required for the full protective effect of small-molecule Hedgehog pathway activation in colitis; this pharmacologic augmentation of Hedgehog pathway activity and stromal IL-10 expression are associated with increased presence of CD4+Foxp3+ regulatory T cells. We thus identify stromal cells as cellular coordinators of colon inflammation and suggest their pharmacologic manipulation as a potential means to treat colitis.

Small-molecule Hedgehog inhibitor attenuates the leukemia-initiation potential of acute myeloid leukemia cells.

Aberrant activation of the Hedgehog signaling pathway has been implicated in the maintenance of leukemia stem cell populations in several model systems. PF‐04449913 (PF‐913) is a selective, small‐molecule inhibitor of Smoothened, a membrane protein that regulates the Hedgehog pathway. However, details of the proof‐of‐concept and mechanism of action of PF‐913 following administration to patients with acute myeloid leukemia (AML) are unclear. This study examined the role of the Hedgehog signaling pathway in AML cells, and evaluated the in vitro and in vivo effects of the Smoothened inhibitor PF‐913. In primary AML cells, activation of the Hedgehog signaling pathway was more pronounced in CD34+ cells than CD34− cells. In vitro treatment with PF‐913 induced a decrease in the quiescent cell population accompanied by minimal cell death. In vivo treatment with PF‐913 attenuated the leukemia‐initiation potential of AML cells in a serial transplantation mouse model, while limiting reduction of tumor burden in a primary xenotransplant system. Comprehensive gene set enrichment analysis revealed that PF‐913 modulated self‐renewal signatures and cell cycle progression. Furthermore, PF‐913 sensitized AML cells to cytosine arabinoside, and abrogated resistance to cytosine arabinoside in AML cells cocultured with HS‐5 stromal cells. These findings imply that pharmacologic inhibition of Hedgehog signaling attenuates the leukemia‐initiation potential, and also enhanced AML therapy by sensitizing dormant leukemia stem cells to chemotherapy and overcoming resistance in the bone marrow microenvironment.

Co-delivery of small molecule hedgehog inhibitor and miRNA for treating liver fibrosis

In liver fibrosis, secretion of growth factors and hedgehog (Hh) ligands by hepatic parenchyma upon repeated insults results in transdifferentiation of quiescent hepatic stellate cells (HSCs) into active myofibroblasts which secrete excessive amounts of extracellular matrix (ECM) proteins. An Hh inhibitor GDC-0449 and miR-29b1 can play an important role in treating liver fibrosis by inhibiting several pro-fibrotic genes. Our in-silico analysis indicate that miR-29b1 targets several profibrotic genes like collagen type I & IV, c-MYC, PDGF-β and PI3K/AKT which are upregulated in liver fibrosis. Common bile duct ligation (CBDL) resulted in an increase in Ptch-1, Shh and Gli-1 expression. miR-29b1 and GDC-0449 were co-formulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol-graft-tetraethylenepentamine) (mPEG-b-PCC-g-DC-g-TEPA) copolymer, and injected systemically into CBDL mice. High concentrations of GDC-0449 and miR-29b1 were delivered to liver cells as determined by in situ liver perfusion at 30 min post systemic administration of their micelle formulation. There was a significant decrease in collagen deposition in the liver and serum injury markers, leading to improvement in liver morphology. Combination therapy was more effective in providing hepatoprotection, lowering liver injury related serum enzyme levels, reducing fibrotic protein markers such as collagen, α-SMA, FN-1 and p-AKT compared to monotherapy. In conclusion, inhibition of Hh pathway and restoration of miR-29b1 have the potential to act synergistically in treating CBDL-induced liver fibrosis in mice.

Codelivery of small molecule hedgehog inhibitor and miRNA for treating pancreatic cancer.

Successful treatment of pancreatic ductal adenocarcinoma (PDAC) remains a challenge due to the desmoplastic microenvironment that promotes both tumor growth and metastasis and forms a barrier to chemotherapy. Hedgehog (Hh) signaling is implicated in initiation and progression of PDAC and also contributes to desmoplasia. While Hh levels are increased in pancreatic cancer cells, levels of tumor suppressor miR-let7b, which targets several genes involved in PDAC pathogenesis, is downregulated. Therefore, our overall objective was to inhibit Hh pathway and restore miR-let7b simultaneously for synergistically treating PDAC. miR-let7b and Hh inhibitor GDC-0449 could inhibit the proliferation of human pancreatic cancer cells (Capan-1, HPAF-II, T3M4, and MIA PaCa-2), and there was synergistic effect when miR-let7b and GDC-0449 were coformulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl- 2-carboxyl-propylenecarbonate-graft-dodecanol-graft-tetraethylene-pentamine) (mPEG-b-PCC-g-DC-g-TEPA). This copolymer self-assembled into micelles of <100 nm and encapsulated hydrophobic GDC-0449 into its core with 5% w/w drug loading and allowed complex formation between miR-let7b and its cationic pendant chains. Complete polyplex formation with miRNA was observed at the N/P ratio of 16/1. Almost 80% of GDC-0449 was released from the polyplex in a sustained manner in 2 days. miRNA in the micelle formulation was stable for up to 24 h in the presence of serum and high uptake efficiency was achieved with low cytotoxicity. This combination therapy effectively inhibited tumor growth when injected to athymic nude mice bearing ectopic tumor generated using MIA PaCa-2 cells compared to micelles carrying GDC-0449 or miR-let7b alone. Immunohistochemical analysis revealed decreased tumor cell proliferation with increased apoptosis in the animals treated with miR-let7b and GDC-0449 combination.

Current landscape for treatment of advanced basal cell carcinoma.

Basal cell carcinomas (BCCs) account for around 80% of non-melanoma skin cancer. Australia has the highest incidence of BCC globally and the rates continue to increase in both Australia and New Zealand. BCC causes significant morbidity, placing an enormous burden on the healthcare system. Treatment of patients with advanced BCC can be particularly challenging. A panel of UK experts recently defined advanced disease as BCC that in which current treatment modalities are considered potentially contraindicated by clinical or patient-driven factors. Research has found that mutations in the hedgehog signalling pathway underpin the pathogenesis of the vast majority of sporadic BCC, as well as Gorlin syndrome. The first-in-class oral small molecule hedgehog pathway inhibitor - vismodegib-is now approved in a number of countries for use in locally-advanced and metastatic BCC and has resulted in improved outcomes in the majority of patients treated. With a number of similar agents in the pipeline, research is now focusing on identifying mechanisms that may contribute to resistance to this agent in some lesions.

Abstract 3873: Hedgehog signaling maintains gastric cancer stem cells and promotes chemotherapy resistance: results from laboratory and clinical studies

Abstract Introduction: Gastric cancers may harbor a small subset of cancer stem cells (CSCs) with the exclusive ability to self-renew and differentiate into heterogenous cell types. These CSCs may also contribute to chemotherapy resistance. The Hedgehog (HH) pathway is a key developmental pathway that can be subverted by CSCs during tumorigenesis. However in a recent randomized phase II trial of chemotherapy with or without the small molecule HH inhibitor vismodegib for advanced gastric cancers, the addition of vismodegib did not increase progression-free survival (PFS) or overall survival (OS). In this study, we examine the role of HH signaling in gastric CSC maintenance and chemotherapy resistance. Methods and Results: Gastric cancer cell lines AGS, MKN-45, and NCI-N87 were grown as spheroids to enrich for CSCs. Spheroid cells were found to have upregulation of the putative gastric CSC marker CD44 along with HH pathway proteins Shh, Ptch1, Smo, and Gli1. Inhibition of the HH signaling using Smo shRNA or vismodegib decreased spheroid formation by 70.3-78.4% or 66.9-70.8%, respectively, and attentuated another CSC phenotype, single cell colony formation, by 66.9-78.4%. Transformation phenotypes such as migration, invasion, and anchorage-independent colony formation were also inhibited in gastric CSCs by 50.2-65.6%, 57.4-66.3%, and 3.8-4.6 fold, respectively. CD44(+) gastric CSCs from all 3 cell lines were resistant to 5-fluorouracil or cisplatin chemotherapy, and this resistance was reversed with the addition of Smo shRNA or vismodegib. The combination of Smo shRNA and cisplatin synergistically blocked the growth of MKN-45 xenografts, and treated tumors demonstrated a 1.8-2.6 fold increase in tumor cell apoptosis compared to tumors treated with cisplatin alone. Clinical tumor samples from the phase II vismodegib trial were analyzed for CD44 expression (as a surrogate to levels of CSCs). In the chemotherapy alone group, high CD44 expression was associated with worse PFS and OS. However in the chemotherapy with vismodegib group, high CD44 expression was associated with improved PFS and OS. For two patients in the vismodegib arm of the study who had a complete response, CD44 levels were 6.1-fold higher than the other patients in the group (p=0.001). Conclusions: HH signaling is required to maintain gastric CSC phenotypes such as spheroid formation and colony formation from single cells as well malignant transformation phenotypes such as migration, invasion, and anchorage-independent growth. Gastric CSCs are resistant to chemotherapy compared to unselected cells, and HH inhibition can reverse this resistance. Given gastric cancer is a heterogeneous disease, the strategy of combining chemotherapy with HH inhibition may only be effective in a subset of gastric cancer patients with high levels of CD44(+) gastric CSCs. Citation Format: Changhwan Yoon, Do Joong Park, Benjamin Schmidt, Nicholas J. Thomas, Hae-June Lee, Teresa S. Kim, Yelena Y. Janjigian, Deirdre J. Cohen, Sam S. Yoon. Hedgehog signaling maintains gastric cancer stem cells and promotes chemotherapy resistance: results from laboratory and clinical studies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3873. doi:10.1158/1538-7445.AM2014-3873

A fast entry to furanoditerpenoid-based Hedgehog signaling inhibitors: identifying essential structural features.

New, small molecule Hedgehog (Hh) pathway inhibitors, such as the furanoditerpenoid taepeenin D, are of high medicinal importance. To establish key structure-activity relationships (SARs) for this lead, a synthetic sequence has been developed for the expedient preparation of several derivatives and their evaluation as Hh inhibitors exploiting its structural similarity to abietic acid. While C(14) substitution is not essential for biological activity, the presence of a hydrogen bond acceptor at C(6) and an intact benzofuran moiety are.

Downregulating Hedgehog Signaling Reduces Renal Cystogenic Potential of Mouse Models

Renal cystic diseases are a leading cause of renal failure. Mutations associated with renal cystic diseases reside in genes encoding proteins that localize to primary cilia. These cystoproteins can disrupt ciliary structure or cilia-mediated signaling, although molecular mechanisms connecting cilia function to renal cystogenesis remain unclear. The ciliary gene, Thm1(Ttc21b), negatively regulates Hedgehog signaling and is most commonly mutated in ciliopathies. We report that loss of murine Thm1 causes cystic kidney disease, with persistent proliferation of renal cells, elevated cAMP levels, and enhanced expression of Hedgehog signaling genes. Notably, the cAMP-mediated cystogenic potential of Thm1-null kidney explants was reduced by genetically deleting Gli2, a major transcriptional activator of the Hedgehog pathway, or by culturing with small molecule Hedgehog inhibitors. These Hedgehog inhibitors acted independently of protein kinase A and Wnt inhibitors. Furthermore, simultaneous deletion of Gli2 attenuated the renal cystic disease associated with deletion of Thm1. Finally, transcripts of Hedgehog target genes increased in cystic kidneys of two other orthologous mouse mutants, jck and Pkd1, and Hedgehog inhibitors reduced cystogenesis in jck and Pkd1 cultured kidneys. Thus, enhanced Hedgehog activity may have a general role in renal cystogenesis and thereby present a novel therapeutic target.

Embryofetal Development Study of Vismodegib, a Hedgehog Pathway Inhibitor, in Rats

Vismodegib (Erivedge) is a first-in-class small-molecule hedgehog pathway inhibitor for the treatment of adults with advanced basal-cell carcinoma. Because this pathway is known to play key roles in patterning and growth during vertebrate development, vismodegib was anticipated to be embryotoxic. To support marketing applications, an embryofetal development study was completed in which a limited number of pregnant rats (n = 6/group) was administered vismodegib by oral gavage on gestation days 6 to 17. When vismodegib was administered at ≥60 mg/kg/day, doses associated with evidence of pharmacologic activity in previous rat toxicity studies, all conceptuses were resorbed at an early embryonic stage in the absence of significant maternal toxicity. When administered at 10 mg/kg/day, corresponding to an exposure (AUC0-24h ) approximately 15% of the median in patients at steady state, a variety of malformations were observed, including absent/fused digits in the hindlimb of multiple fetuses, multiple craniofacial abnormalities in one fetus, and an anorectal defect in one fetus. In addition, the incidence of variations, including dilated renal pelvis or ureter and incompletely or unossified skeletal elements, was significantly greater when compared with the controls. These results confirmed that vismodegib is likely to be embryotoxic at clinically relevant maternal exposures, and doses ≥60 mg/kg/day resulted in a 100% incidence of embryolethality that likely resulted from severe defects in early embryonic development. In contrast, craniofacial defects typically associated with hedgehog pathway inhibition were only observed in one fetus at the low dose of 10 mg/kg/day, which likely reflected minimal or intermittent pathway inhibition at low exposures.

Investigations into the Mechanisms of Pyridine Ring Cleavage in Vismodegib

Vismodegib (Erivedge, GDC-0449) is a first-in-class, orally administered small-molecule Hedgehog pathway inhibitor that is approved for the treatment of advanced basal cell carcinoma. Previously, we reported results from preclinical and clinical radiolabeled mass balance studies in which we determined that metabolism is the main route of vismodegib elimination. The metabolites of vismodegib are primarily the result of oxidation followed by glucuronidation. The focus of the current work is to probe the mechanisms of formation of three pyridine ring-cleaved metabolites of vismodegib, mainly M9, M13, and M18, using in vitro, ex vivo liver perfusion and in vivo rat studies. The use of stable-labeled ((13)C2,(15)N)vismodegib on the pyridine ring exhibited that the loss of carbon observed in both M9 and M13 was from the C-6 position of pyridine. Interestingly, the source of the nitrogen atom in the amide of M9 was from the pyridine. Evidence for the formation of aldehyde intermediates was observed using trapping agents as well as (18)O-water. Finally, we conclude that cytochrome P450 is involved in the formation of M9, M13, and M18 and that M3 (the major mono-oxidative metabolite) is not the precursor for the formation of these cleaved products; rather, M18 is the primary cleaved metabolite.

Harnessing Hedgehog for the Treatment of Basal Cell Carcinoma

Vismodegib, a first-in-class small-molecule hedgehog pathway inhibitor, was approved by the Food and Drug Administration in January 2012 for the treatment of metastatic and locally advanced basal cell carcinoma (BCC). The commentary by Wysong et al1 in this issue of JAMA Dermatology highlights the poor response of metastatic BCC to conventional forms of therapy, making hedgehog pathway antagonists an important addition to the therapeutic armamentarium for this rare but deadly type of BCC.

Abstract SY02-04: Inhibition of Hedgehog signaling for prevention and treatment of basal cell carcinomas.

Abstract Basal cell carcinomas, the most common of human cancers, differ from many other cancers not only in their frequency but also in the great rarity with which they metastasize and their routinely high cure rate following surgery. Because all BCCs are driven by mutational activation of the hedgehog signaling pathway in the tumor cells, small molecule hedgehog inhibitors are a “natural” approach. Indeed, not only the rare metastatic and locally advanced BCCs but also the high number of smaller individually less aggressive BCCs in patients with the Gorlin syndrome respond extremely well to small molecule Hedgehog inhibitors. This illustrates that interfering with critical pathways not only can treat existing tumors but also can prevent even the development of new tumors. Citation Format: Ervin H. Epstein. Inhibition of Hedgehog signaling for prevention and treatment of basal cell carcinomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr SY02-04. doi:10.1158/1538-7445.AM2013-SY02-04

Potent small molecule Hedgehog agonists induce VEGF expression in vitro

Here, we describe the synthesis, SAR studies as well as biological investigations of the known Hedgehog signaling agonist SAG and a small library of its analogues. The SAG and its derivatives were analyzed for their potency to activate the expression of the Hh target gene Gli1 in a reporter gene assay. By analyzing SAR important molecular descriptors for Gli1 activation have been identified. SAG as well as compound 10c proven to be potent activators of VEGF expression in cultivated dermal fibroblasts. Importantly and in contrast to SAG, derivative 10c displayed no toxicity in concentrations up to 250μm.

Medical Management of Basal Cell Carcinoma with a Small-Molecule Hedgehog Inhibitor

Most basal cell carcinomas (BCCs) are removed surgically; a few are treated with radiation or topical therapies. Mutations in the PTCH1 gene, a member

Combination of Hedgehog Signaling Blockage and Chemotherapy Leads to Tumor Reduction in Pancreatic Adenocarcinomas

Activation of the hedgehog signal transduction pathway, triggered by hedgehog binding to the transmembrane receptor patched 1 (PTCH1) or by mutations in the PTCH1 gene, plays an important role in the development of various tumors. To investigate whether the Hedgehog signaling pathway is also active in human pancreatic adenocarcinomas, we determined the expression levels of the known Hedgehog target genes PTCH1 and GLI-1 in pancreatic tumors. To determine whether alterations in the PTCH1 gene are responsible for this pathway activation, we screened pancreatic carcinomas for mutations in PTCH. To investigate the contribution of hedgehog signaling to the tumorigenicity of pancreatic tumor cells, we blocked the Hedgehog pathway in cultured tumor cells and xenografts using the steroidal alkaloid cyclopamine and the small-molecule Hedgehog inhibitor Hh-Antag. We identified single nucleotide polymorphisms (SNPs) within the PTCH1 gene but no somatic PTCH1 mutations. Pathway-blockage resulted in a significant dose-dependent reduction of tumor cell growth in vitro and in vivo. Moreover, combined treatment with cyclopamine and the conventional antimetabolite gemcitabine revealed a synergistic effect on the reduction of tumor growth in pancreatic adenocarcinoma xenografts. Inhibition of Hedgehog signaling could be a promising approach for the treatment of pancreatic adenocarcinomas.

Abstract B188: Pharmacokinetic assessment of drug-drug interaction potential when rosiglitazone or combined oral contraceptive is coadministered with vismodegib in patients with locally advanced or metastatic solid tumors.

Abstract Vismodegib is a first-in-class small molecule Hedgehog pathway inhibitor that is being developed for the treatment of advanced basal cell carcinoma. In a previous phase I study for patients with advanced malignancies, vismodegib was well tolerated and tumor regressions were seen in patients with advanced basal cell carcinoma and medulloblastoma. In vitro, vismodegib inhibits CYP2C8 with a Ki of 6.0 μM, which was the most potent relative to other CYP isoforms. With the average steady-state plasma concentration of total vismodegib being approximately 20 μM, inhibition of CYP2C8 by vismodegib may be important when patients are taking drugs known to be metabolized by CYP2C8. Furthermore, while vismodegib was not shown to induce CYP enzymes in vitro, it is a known teratogen. A DDI assessment with combined oral contraceptive (OC) was therefore conducted to ensure efficacious levels of OC would be maintained in patients taking vismodegib and OC in combination. This single-arm study consisted of two cohorts; 24 patients took 4 mg rosiglitazone (a known CYP2C8 substrate) and 27 patients took OC (norethindrone 1 mg/ethinyl estradiol 35 mcg, Ortho-Novum 1/35®). On Day 1 patients took rosiglitazone or OC followed by extensive PK sampling for 24 hrs. From Day 2 to Day 7 patients took 150 mg vismodegib once per day. On Day 8 patients took either vismodegib and rosiglitazone or vismodegib and OC followed by extensive PK sampling for 24 hrs. From Day 9 onward patients took vismodegib until disease progression or lack of benefit. The primary objective of this study was to evaluate the relative effect of vismodegib on AUC and Cmax for rosiglitazone and OC (ethinyl estradiol and norethindrone). The average steady state plasma concentration of total vismodegib (N=51) was 20.6 μM (range, 7.93 − 62.4 μM). There was no clinically meaningful difference in rosiglitazone PK parameters between Day 1 (without vismodegib) and Day 8 (with vismodegib) with a less than 10% difference in AUCinf and Cmax, on average. The geometric mean ratios (GMRs) for rosiglitazone AUC0−inf and Cmax were 93.1 and 93.4 with corresponding 90% confidence intervals (CIs) of (85.0, 102) and (89.4, 97.6), respectively. Concomitant administration of vismodegib with OC did not strongly impact the plasma concentrations of ethinyl estradiol or norethindrone, as evidenced by a less than 20% change in AUCinf and Cmax, on average, for both components. The GMRs for ethinyl estradiol AUC0−inf and Cmax were 99.3 and 106 with corresponding 90% CIs of (91.9, 107) and (94.8, 117), respectively while the GMRs for norethindrone AUC0−inf and Cmax were 124 and 112 with corresponding 90% CIs of (116, 132) and (101, 124), respectively. In the current study, the steady state plasma concentration of total vismodegib was above the in vitro Ki for CYP2C8. In addition, daily dosing of 150 mg vismodegib for 7 days should have been adequate to result in enzyme induction, if applicable. Overall, results from this study indicate that there was no clinically meaningful difference in AUC0−inf and Cmax for rosiglitazone, ethinyl estradiol, or norethindrone when co-administered with vismodegib. Taken together these results suggest that vismodegib can be co-administered with CYP substrates and combined oral contraceptive without the risk of a pharmacokinetic DDI. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B188.