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Tables S1, S2, S3, S4

Figure S2. (A) Change in the tumor burden from baseline over time according to RECIST for all the included patients. The tumor burden was measured as the sum of the longest diameters of target lesions. Each line represents a patient. (B) Kaplan-Meier plot of the overall survival for all the included patients (N =18). (C) Kaplan-Meier plot of the progression-free survival for all the included patients (N =18).

Purpose:In BRAFV600MUT metastatic melanoma, cyclin D–CDK4/6–INK4–Rb pathway alterations are involved in resistance to MAPK inhibitors, suggesting a clinical benefit of cyclin-dependent kinase 4 (CDK4) inhibitors. In this phase I–II study, we aimed to establish the MTD of palbociclib when added to vemurafenib.Patients and Methods:Patients with BRAFV600E/KMUT metastatic melanoma harboring CDKN2A loss and RB1 expression were included and stratified into two groups according to previous BRAF inhibitor treatment (no:strata 1; yes:strata 2). Treatment comprised palbociclib once daily for 14 days followed by a 7-day break + continuous dosing of vemurafenib. The primary endpoint was the occurrence of dose-limiting toxicity (DLT), and the secondary endpoints included the best response, survival, pharmacokinetics, and tumor molecular profiling.Results:Eighteen patients were enrolled, with 15 in strata 2. Characteristics at inclusion were American Joint Committee on Cancer stage IVM1c (N = 16; 88.9%), high lactate dehydrogenase (N = 9; 50.0%), and median number of previous treatments of 2. One and 5 patients experienced DLT in strata 1 and 2, respectively, defining the MTD at palbociclib 25 mg and vemurafenib 960 mg in strata 2. No significant evidence for drug–drug interactions was highlighted. The median progression-free survival was 2.8 months, and 5 (27.8%) patients showed a clinical response. The baseline differential mRNA expression analysis and in vitro data revealed the role of CHEK2 in the response to palbociclib.Conclusions:Although the combination of palbociclib + fixed-dose vemurafenib did not allow an increased palbociclib dosage above 25 mg, a significant clinical benefit was achieved in pretreated patients with melanoma. An association between the transcriptomic data and clinical response was highlighted.

Supplementary Materials and Methods

Figure S4. Differential gene expression analysis in responders vs nonresponders conducted on baseline samples. Three hundred fifty-eight genes were screened. Genes with FDR P-value

Figure S3. DNA alterations (mutations and copy number alterations) uncovered in all samples collected before and during treatment (Baseline, after cycle 2 and end of treatment). * indicates samples processed only in mRNA expression and copy number analysis (no NGS data available).

Figure S1. (A) RNA expression and copy number variations in A375 melanoma cell lines resistant to vemurafenib (A375R). RNA expression was normalized according to PPIA, B2M and ACTB gene expression (siRNA: small interfering RNA). (B) Inhibition of CHEK2 at both the mRNA and protein levels in A375 melanoma cell lines resistant to vemurafenib (A375R) transfected with siRNA CHEK2 (50 nM and 100 nM) compared to those transfected with siRNA control (siRNA: small interfering RNA).

Purpose: In BRAFV600MUT metastatic melanoma, cyclin D–CDK4/6–INK4–Rb pathway alterations are involved in resistance to MAPK inhibitors, suggesting a clinical benefit of cyclin-dependent kinase 4 (CDK4) inhibitors. In this phase I–II study, we aimed to establish the MTD of palbociclib when added to vemurafenib. Patients and Methods: Patients with BRAFV600E/KMUT metastatic melanoma harboring CDKN2A loss and RB1 expression were included and stratified into two groups according to previous BRAF inhibitor treatment (no:strata 1; yes:strata 2). Treatment comprised palbociclib once daily for 14 days followed by a 7-day break + continuous dosing of vemurafenib. The primary endpoint was the occurrence of dose-limiting toxicity (DLT), and the secondary endpoints included the best response, survival, pharmacokinetics, and tumor molecular profiling. Results: Eighteen patients were enrolled, with 15 in strata 2. Characteristics at inclusion were American Joint Committee on Cancer stage IVM1c (N = 16; 88.9%), high lactate dehydrogenase (N = 9; 50.0%), and median number of previous treatments of 2. One and 5 patients experienced DLT in strata 1 and 2, respectively, defining the MTD at palbociclib 25 mg and vemurafenib 960 mg in strata 2. No significant evidence for drug–drug interactions was highlighted. The median progression-free survival was 2.8 months, and 5 (27.8%) patients showed a clinical response. The baseline differential mRNA expression analysis and in vitro data revealed the role of CHEK2 in the response to palbociclib. Conclusions: Although the combination of palbociclib + fixed-dose vemurafenib did not allow an increased palbociclib dosage above 25 mg, a significant clinical benefit was achieved in pretreated patients with melanoma. An association between the transcriptomic data and clinical response was highlighted.

InPatients withEighteen patients were enrolled, with 15 in strata 2. Characteristics at inclusion were American Joint Committee on Cancer stage IVM1c (Although the combination of palbociclib + fixed-dose vemurafenib did not allow an increased palbociclib dosage above 25 mg, a significant clinical benefit was achieved in pretreated patients with melanoma. An association between the transcriptomic data and clinical response was highlighted.

Introduction Parmi les mecanismes de resistance aux inhibiteurs de BRAF (iBRAF), les effecteurs du cycle cellulaire, notamment CDK4, sont impliques dans la reactivation de ERK. Dans cette etude de phase I-II multicentrique en ouvert, notre but etait d’etablir la Dose Maximale Toleree (DMT) du palbociclib (PB), un inhibiteur de CDK4/6, en association au vemurafenib (VM) chez les patients atteints de melanome metastatique et porteurs d’une mutation BRAFV600 ( NCT02202200 ). Materiel et methodes Les patients atteints d’un melanome metastatique mutes BRAFV600E/K presentant une perte de CDKN2A et une expression de RB1 ont ete inclus et ont recu des cycles de 21 jours de traitement associant : 1) une administration quotidienne de PB pendant 21 jours et 2) une administration biquotidienne de VM durant les 14 premiers jours du cycle. Les patients ont ete stratifies en 2 groupes selon la prise anterieure d’un traitement par iBRAF (Non : groupe 1 ; Oui : groupe 2). Les posologies de PB (mg/QD)/VM (mg/BID) allaient de 25/720 a 200/960. Le critere principal etait la survenue d’une toxicite limitant la dose au cours des deux premiers cycles de traitement. Les criteres secondaires comprenaient la meilleure reponse observee (RECIST v1.1), la survie globale (SG), la survie sans progression (SSP), les parametres pharmacocinetiques, le profil moleculaire tumoral initial (analyse transcriptomique). Resultats Dix-huit patients ont ete inclus, dont 15 (83 %) dans le groupe 2. Les principales caracteristiques a l’inclusion etaient : sexe masculin : 11 (61 %), âge median : 55 ans, melanome de stade IIIC non resecable : 2 (11 %), melanome de stade IV : 16 (89 %). Trois (17 %) patients presentaient des metastases cerebrales et 9 (50 %) un niveau de LDH eleve a l’inclusion. Le delai median entre le diagnostic de melanome et l’inclusion etait de 24,5 mois. Une DLT a ete observee pour 1 et 5 patients dans les groupes 1 et 2 respectivement definissant la DMT PB/VM a 25 mg/960 mg dans le groupe 2. Aucune interaction medicamenteuse significative entre PB et VM n’a ete mise en evidence. Dans le groupe 2, 4 (27 %) patients ont presente une reponse clinique et 8 (53 %) patients une maladie stable. La SSP mediane etait de 4,3 mois et la SG mediane de 19,9 mois. L’analyse transcriptomique initiale a revele un taux d’alteration eleve associe a la reponse clinique et un enrichissement des genes impliques dans les voies de la MAP-Kinase, du cycle cellulaire et de l’apoptose. Conclusion L’association au VM n’a pas permis d’augmenter la dose fixe de PB au-dessus de 25 mg. Cependant, un benefice clinique a ete observe chez les patients pretraites et l’analyse moleculaire sur les lesions a l’inclusion a revele une association entre les donnees transcriptomiques et la reponse clinique.

Background: A novel combination of vemurafenib (VM), a selectif inhibitor of BRAF V600 mutated protein + oral palbociclib (Palbo) a highly selective reversible oral inhibitor of cyclin-dependent kinases (CDK) 4 and 6, could provide a synergistic antitumor activity in patients with metastatic melanoma harbouring BRAF V600 mutation and CDKN2A loss. VM has been shown to be an inductor of CYP3A4 which is also mainly involved in Palbo metabolism. In this study we investigated the potential pharmacokinetic (PK) drug-drug interactions (DDI) related to the association of VM and Palbo. Methods: metastatic melanoma harbouring BRAF V600 mutation and CDKN2A loss patients were treated with a 14 days on followed by 7 days off dosing schedule of Palbo + continuous bid dosing of VM. Dose levels [DL, Palbo (mg/day)/VM (mg/bid)] ranged from 25/720 to 200/960. For PK analysis, 7 time point samples were collected on D1C1, D21C1, and D7C2, for Palbo and VM assays. Plasma concentrations of Palbo and VM, were measured using ultra high performance liquid chromatography (UHPLC) coupled with tandem mass spectrometry validated methods. Population PK (PPK) was modeled using a non linear mixed effect model program (Monolix version 2018r) by computing the maximum likelihood estimator of the parameters without any approximation of the model (no linearization). The following parameters were calculated absorption constant (Ka); apparent distribution volume (V/F); apparent clearance (CL/F) Results: A total of 18 patients were treated by the combination of Palbo + VM. VM and palbo plasma concentrations were measured in 236 and 275 blood samples respectively. A one-compartment open model with linear elimination adequately described Palbo concentration-time courses. The inter-individual variabilities (ISV) could be well estimated for all stuctural parameters. The PPK parameters obtained for the structural model were: Ka = 0.791 h-1, CL/F=76.0L/h, V1/F=2830 L. Albuminemia had a significant impact on palbo CL. A one-compartment model adequately fitted the VM plasma concentration-time data. The PPK parameters were CL/F=0.133 L/h, V/F=83.6 L and Ka has been fixed at 0.2 h-1. Body weight (BW) was the best size descriptor when VM CL and V terms were normalized to a mean BW of 70 Kg according to an allometric scaling rule. Conclusions: The PPK modeling satisfactorily described the plasma Plabo and VM time-concentration curves in patients. The main covariate effect was related to BW and albuminemia. There is no significant evidence for drug-drug PK interaction between Palbo and VM. PK-PD modeling will be performed. Citation Format: Samuel Huguet, Thierry Lesimple, Arthur Geraud, Mouna Amini-Adle, Caroline Dutriaux, Laetitia Da Meda, Florence Capelle, Zineb Ghrieb, Samia Mourah, Olivier Madar, Didier Bouton, Mathieu Resche-Rigon, Celest Lebbe, Keyvan Rezai. A phase I-II pharmacokinetic drug-drug interaction evaluation of oral palbociclib in combination with vemurafenib in patients suffering metastatic melanoma with BRAF V600 mutated and CDKN2A loss & expression of Rb [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3895.

9545 Background: Among mechanisms of resistance to BRAF inhibitors (BRAFi), cell cycle effectors including CDK4 have been involved in ERK reactivation. In this phase I-II open label study, we aimed to establish the Maximum Tolerated Dose (MTD) of PD0332991, an inhibitor of CDK4/6, when added to vemurafenib (VM) in metastatic melanoma patients. Methods: Patients with BRAFV600E/K mutated metastatic melanoma harbouring CDKN2A loss and RB1 expression were included. Patients were treated with a 14 days followed by 7 days rest daily dosing schedule of PD0332991 + continuous BID dosing of VM, and stratified into 2 groups according to previous BRAFi treatment (no group 1, yes group 2). Dose levels (PD0332991 (mg/QD)/VM (mg/BID) ranged from 25/720 to 200/960. The primary endpoint was the occurrence of a DLT within the first 2 cycles of therapy. Secondary endpoints included best response (RECIST), OS, PFS, pharmacokinetics parameters, tumour molecular profiling on baseline lesions using transcriptomic and NGS analysis. Results: Nineteen patients were enrolled, among them 16 (84%) in group 2, with 18.5 months median follow-up. Characteristics at baseline were: male 11 (58%), median age 54.4 years, unresectable stage IIIC 2 (11%), stage IV 17 (89%), M1C 12 (67%), high LDH 9 (47%), median time from advanced melanoma diagnosis to inclusion 26.8 months, ≥ 2 lines therapy 13 (68%). A DLT was observed for 1 and 5 patients in group 1 and 2 respectively, defining the MTD at PD0332991 25mg and VM 960mg in group 2. No significant evidence for drug-drug interaction between PD0332991 and VM was highlighted. In group 2, ORR was estimated to 4 (25%), SD to 8 (50%), median PFS to 9.3 months and median OS to 13.2 months. Baseline transcriptomic analysis revealed high alteration rate associated with clinical response and enrichment in genes related to MAPK, cell cycle and apoptosis pathways. Conclusions: While combination of fixed dose of PD0332991 + VM did not allow us to increase PD0332991 dosage above 25mg, significant clinical benefit was achieved in heavily pretreated patients; baseline molecular analysis revealed an association between transcriptomic data and clinical response. Clinical trial information: NCT02202200.

With specific liver X receptor α and β (LXRα and LXRβ) antibodies, we found that LXRα is strongly expressed in the luminal and basal cells of prostatic epithelium. The ventral prostates (VP) of LXRα −/− mice are characterized by the presence of smooth-muscle actin-positive stromal overgrowth around the prostatic ducts and by numerous fibrous nodules pushing into the ducts and causing obstruction, so that most of the ducts were extremely dilated. BrdU labeling and Ki67 staining revealed epithelial and stromal proliferation in the fibrous nodules. However, the dense stroma surrounding the ducts was not positive for proliferation markers. There was no detectable difference between WT and LXRα −/− mice VP in the expression of the androgen receptor, but there was an increase in nuclear expression of Snail and Smad 2/3, indicating enhanced TGF-β signaling. Upon treatment of WT mice for 3 months with the LXR agonist T2320 or for 3 weeks with β-sitosterol, LXRα was downregulated, and a VP phenotype similar to that of LXRα −/− mice resulted. We conclude that in rodents, LXRα seems to control VP stromal growth and that LXRα −/− mice may be a useful model to study prostatic stromal hyperplasia. Because LXRα is expressed in the epithelium, the excessive stromal growth in LXRα −/− mice indicates that LXRα is essential for epithelial stromal communication.

Liver X receptor (LXR) β regulates cholesterol levels in the brain and is essential for maintenance of motor neurons in the spinal cord and dopaminergic neurons in the substantia nigra. Here, we have examined the expression pattern of LXRβ protein in the cerebral cortex and looked for defects in cortical development in LXRβ knockout (LXRβ −/− ) mice. LXRβ protein was widely expressed in the mouse brain at later embryonic stages, and the expression pattern in the cerebral cortex was developmentally regulated. In normal postnatal mice, LXRβ was localized mainly in the upper layers of the cerebral cortex. In LXRβ −/− mice layers II and III were thinner with fewer neurons. Layer I was slightly thicker, whereas layers IV–VI were essentially normal. Consistent with this finding, Brn2 and NeuN expression were decreased in the upper layers in the LXRβ −/− neonatal cortex. The number of S-phase progenitor cells in the cortex between embryonic day (E) 12.5 to E16.5, was similar in WT and LXRβ −/− littermates but BrdU birth dating revealed that late-generated neurons labeled by BrdU injections administered at E14.5 or E16.5, and destined to cortical layers II/III, were disorganized and failed to migrate. The defect in migration appears to be caused by a reduction in the number of vertical processes emanating from the radial glia. These processes are the architectural guides for later-born migrating neurons. Taken together, these findings suggest that LXRβ expression in the cerebral cortex is involved in cortex lamination and is essential for the migration of late-generated neocortical neurons.

Many autoimmune diseases including rheumatoid arthritis (RA), Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE) occur much more frequently in women than in men. There is much evidence that oestrogen is the major cause of this gender difference. Interestingly, oestrogen relieves the symptoms of RA and SS but it exacerbates SLE. This contradictory effect of oestrogen on autoimmune diseases is not well understood. Most of the effects of oestrogen are mediated by two receptors: oestrogen receptor alpha and beta (ERalpha and ERbeta). To determine whether these contradictory effects of oestrogen relate to the involvement of distinct effects of the two ERs, we investigated expression of ERalpha and ERbeta in human secondary lymphoid tissues. We observed that, in tonsils, ERbeta is expressed in lymphocytes of germinal centres (GC) and the follicular mantle zone as well as in granulocytes, while ERalpha is expressed only in activated germinal centres but not in the follicular zone. ERbeta is the predominant ER in human leucocytes from peripheral blood, spleen and in leucocytes infiltrating cancers in both males and females. In addition, in different human lymphoma cell lines including Hodgkin lymphoma, Burkitt lymphoma, and multiple myeloma, ERbeta is abundant while ERalpha is not detectable. Our results indicate that ERbeta is the predominant type of ER in mature lymphocytes. We suggest that ERalpha and ERbeta have distinct roles in secondary lymphoid tissues and that further studies with ERbeta-specific agonists will help to elucidate the role of ERbeta in these tissues.

Retinoid X receptors (RXR) are members of the nuclear receptor superfamily of ligand-activated transcription factors that have been characterized in a wide variety of metazoan phyla. They act as heterodimer partners of other nuclear receptors, and in vertebrates also activate transcription as homodimers in the presence of a ligand, 9-cis retinoic acid. In order to test the hypothesis that retinoic acid signaling pathways involving RXRs are present in the Lophotrochozoa, we have sought to isolate conserved members of this family from the platyhelminth parasite Schistosoma mansoni and its intermediate host, the mollusk Biomphalaria glabrata. Here we report that an RXR ortholog from B. glabrata (BgRXR) is better conserved, compared with mouse RXRα, both in the DNA-binding domain (89% identity) and in the ligand-binding domain (LBD) (81% identity), than are arthropod homologs. In EMSA, BgRXR binds to the direct repeat response element DR1 as a homodimer or as a heterodimer with mammalian RARα, LXR, FXR or PPARα. When transfected alone into mammalian cell lines, BgRXR transactivated transcription of a reporter gene from the Apo-A1 promoter in the presence of 9-cis retinoic acid or DHA. Constructs with the Gal4 DNA binding domain fused to the hinge and LBDs of BgRXR were used to show that ligand-dependent activation of transcription by BgRXR required its intact AF-2 activation domain, and that the LBD can form homodimers. Finally, the binding of 9-cis retinoic acid preferentially protected the LBD of BgRXR from degradation by trypsin in a proteolysis protection assay. Our results show that BgRXR binds and is activated by retinoids and suggest that retinoid signaling pathways are conserved in the Lophotrochozoa. The nucleotide sequence reported in this paper has been submitted to the GenBank/EBI Data Bank with accession no. AY048663.

The fushi tarazu factor 1 (FTZ-F1) nuclear receptor subfamily comprises orphan receptors with crucial roles in development and sexual differentiation in vertebrates and invertebrates. We describe the structure and functional properties of an FTZ-F1 from the platyhelminth parasite of humans, Schistosoma mansoni, the first receptor from this family to be characterized in a Lophotrochozoan. It contains a well conserved DNA-binding domain (55–63% identity to other family members) and a poorly conserved ligand-binding domain (20% identity to that of zebrafish FF1a). However, both the ligand domain signature sequence and the activation function 2-activation domain (AF2-AD) are perfectly conserved. Phylogenetic analysis confirmed that SmFTZ-F1 is a member of nuclear receptor subfamily 5, but that it clustered with the Drosophila receptor DHR39 and has consequently been named NR5B1. The gene showed a complex structure with 10 exons and an overall size of 18.4 kb. Two major transcripts were detected, involving alternative promoter usage and splicing of the two 5′ exons, but which encoded identical proteins. SmFTZ-F1 mRNA is expressed at all life-cycle stages with the highest amounts in the larval forms (miracidia, sporocysts and cercariae). However, expression of the protein showed a different pattern; low in miracidia and higher in adult male worms. The protein bound the same monomeric response element as mammalian SF-1 (SF-1 response element, SFRE) and competition experiments with mutant SFREs showed that its specificity was identical. Moreover, SmFTZ-F1 transactivated reporter gene transcription from SFRE similarly to SF-1. This functional conservation argues for a conserved biological role of the FTZ-F1 nuclear receptor family throughout the metazoa.

We describe the cloning and functional characterization of Schistosoma mansoni retinoid-X-receptor (SmRXR; NR2B4-B), a novel member of the nuclear receptor superfamily from S. mansoni, a homologue of vertebrate retinoid-X-receptor. The DNA-binding C domain of SmRXR shows 80% sequence identity to both human RXRalpha and Drosophila ultraspiracle (USP), but a much lower level of conservation of the ligand-binding E domain (22-25% identity). Phylogenetic analysis places SmRXR within the RXR group as an early offshoot of this clade. SmRXR mRNA is expressed at all life-cycle stages but at higher levels in the free-living larval stages. However, the SmRXR protein is expressed at markedly different levels, being almost absent from eggs while present at the highest concentration in schistosomula. Recombinant SmRXR fails to bind to the consensus direct repeat response elements, either alone, or as a heterodimer with mouse retinoic acid receptor alpha or the Drosophila ecdysone receptor. However, the use of chimaeric constructions shows that the C domain of SmRXR will bind to conventional response elements as a heterodimer, and that its specificity is modified by the presence of the D and E domains. In accordance with these results, native SmRXR failed to transactivate the transcription of a reporter gene after cotransfection of mammalian cell lines.

The nuclear receptor (NR) superfamily includes, in addition to ligandactivated transcription factors, members called orphan receptors, for which no ligand has yet been identified. Phylogenetic analysis shows that the nuclear receptor superfamily can be split into six subfamilies. Interestingly, there appears to be no relationship between the position of a given liganded receptor in the tree and the chemical nature of its ligand. For example, RAR and RXR, which both recognize retinoids, belong to two different subfamilies, suggesting an independence between the evolutionary history of the receptors and their ligand binding abilities. A PCR screen for the presence of NR genes in several phyla of early- and nonmetazoan organisms suggests that NR are specific to metazoans and also reveals that the NR genes in Hydra or Anemonia appear to be limited to homologues of orphan receptors. Taken together these data suggest that the first members of the superfamily were probably orphan receptors that later on gained the ability to bind a ligand. Finally, we observed that SmFTZ-F1 and SmRXR are expressed at different levels along the life cycle of the parasitic flatworm Schistosoma mansoni . This suggests that these receptors may play a role in the control of the development of this organism.

Liver X receptors (LXRs) α and β are nuclear oxysterol receptors with a key role in cholesterol, triglyceride, and glucose metabolism. In LXRβ −/− mice on a normal diet, there is a reduction in size of perigonadal fat pad and, on high-fat diet there is resistance to obesity. In the present study, we investigated the reason for the resistance of LXRβ −/− mice to weight gain. In LXRβ −/− mice we found pancreatic exocrine insufficiency with reduced serum levels of amylase and lipase, reduced proteolytic activity in feces, chronic inflammatory infiltration, and, in the ductal epithelium, an increased apoptosis without compensatory proliferation. Electron microscopy revealed ductal dilatation with intraductal laminar structures characteristic of cystic fibrosis. To investigate the relationship between LXRβ and pancreatic secretion, we studied the expression of LXRβ and the water channel, aquaporin-1 (AQP1), in the ductal epithelium of the pancreas. In WT mice, ductal epithelial cells expressed LXRβ in the nuclei and AQP1 on the plasma membrane. In LXRβ −/− mice neither LXRβ nor AQP1 was detectable. Moreover, in WT mice the LXR agonist (T2320) increased AQP1 gene expression. These data demonstrate that in LXRβ −/− mice dietary resistance to weight gain is caused by pancreatic insufficiency and that LXRβ regulates pancreatic exocrine secretion through the control of AQP1 expression. Pancreatic exocrine insufficiency is the main cause of malabsorption syndrome responsible for weight loss in adults and growth failure in children. Several genes are known to be involved in the pathogenesis and susceptibility to pancreatic insufficiency. LXRβ should be included in that list.

International audience; A substantial but disparate body of evidence suggests that hormones affect the development of schistosomes within their definitive hosts. Here, Raymond Pierce and colleagues review such evidence for host steroid and thyroid hormones, and for ecdysteroids, and link this to the expanding knowledge of the nuclear receptors for these hormones. Phylogenetic analysis of the nuclear receptor superfamily and the characterization of the first schistosome nuclear receptors suggest that steroids and thyroid hormone probably act indirectly, or by pathways not involving the control of gene transcription. However, the probability that schistosome nuclear receptors exist for a variety of unique ligands opens up exciting possibilities for targeted drug development.