Efficacy benefit of an NK1 receptor antagonist (NK1RA) in patients receiving carboplatin: supportive evidence with NEPA (a fixed combination of the NK1 RA, netupitant, and palonosetron) and aprepitant regimens.

PURPOSE: Antiemetic guideline recommendations are inconsistent as to whether a neurokinin-1 receptor antagonist (NK1 RA) should be administered with a 5-hydroxytryptamine-3 (5HT3) RA + dexamethasone (DEX) in patients receiving carboplatin. Patients receiving cisplatin routinely receive an NK1 RA-containing regimen with a resulting 14-22 % benefit in no emesis rates over a 5-HT3 RA/DEX control. Recent studies suggest a similar benefit in patients receiving carboplatin. NEPA is the first fixed antiemetic combination agent and comprises the highly selective NK1 RA, netupitant, and pharmacologically distinct 5-HT3 RA, palonosetron (PALO). This paper presents the efficacy of NEPA in the subset of patients receiving carboplatin in a phase 3 trial (NCT01376297), in the context of aprepitant (APR) data in the carboplatin setting. METHODS: One hundred ninety-six patients (47 % of all study patients: n = 145 NEPA + DEX; n = 51 APR + PALO + DEX) received carboplatin in a multinational, double-blind, randomized phase 3 study. Complete response (CR: no emesis/rescue) and no significant nausea (NSN: score ≤25 on 100 mm visual analog scale) rates were calculated. RESULTS: Cycle 1-4 overall (0-120 h) CR rates were similar for NEPA (80, 91, 92, and 93 %) and APR (82, 88, 88, and 90 %). Overall NSN rates were also similar (NEPA 84-96 %; APR 82-90 %). CONCLUSIONS: Response rates for NEPA and APR regimens were similar and consistent with prior studies evaluating the contribution of adding NK1 RAs in patients receiving carboplatin. Considering such evidence, guideline groups/practitioners should consider giving a NK1 RA antiemetic triplet in patients receiving carboplatin.

Drug-drug interaction profile of components of a fixed combination of netupitant and palonosetron: Review of clinical data.

Neurokinin-1 (NK1) receptor antagonists (RAs) are commonly coadministered with serotonin (5-HT3) RAs (e.g. palonosetron (PALO)) to prevent chemotherapy-induced nausea/vomiting. Netupitant/palonosetron (NEPA), an oral fixed combination of netupitant (NETU)-a new NK1 RA-and PALO, is currently under development. In vitro data suggest that NETU inhibits CYP3A4 and is a substrate for and weak inhibitor of P-glycoprotein (P-gp). This review evaluates potential drug-drug interactions between NETU or NEPA and CYP3A4 substrates/inducers/inhibitors or P-gp substrates in healthy subjects. Pharmacokinetic (PK) parameters were evaluated for each drug when NETU was coadministered with PALO (single doses) and when single doses of NETU or NEPA were coadministered with CYP3A4 substrates (erythromycin (ERY), midazolam (MID), dexamethasone (DEX), or oral contraceptives), inhibitors (ketoconazole (KETO)), or inducers (rifampicin (RIF)), or a P-gp substrate (digoxin (DIG)). Results showed no relevant PK interactions between NETU and PALO. Coadministration of NETU increased MID and ERY exposure and significantly increased DEX exposure in a dose-dependent manner; NETU exposure was unaffected. NEPA coadministration had no clinically significant effect on oral contraception, although levonorgestrel exposure increased. NETU exposure increased after coadministration of NEPA with KETO and decreased after coadministration with RIF; PALO exposure was unaffected. NETU coadministration did not influence DIG exposure. In conclusion, there were no clinically relevant interactions between NETU and PALO, or NEPA and oral contraceptives (based on levonorgestrel and ethinylestradiol exposure). Coadministration of NETU or NEPA with CYP3A4 inducers/inhibitors/substrates should be done with caution. Dose reduction is recommended for DEX. Dose adjustments are not needed for NETU coadministration with P-gp substrates.

Neoplastic transformation induced by the gep oncogenes involves the scaffold protein JNK-interacting leucine zipper protein.

The activated mutants of the α-subunits of G proteins G(12) and G(13) have been designated as the gep oncogenes owing to their ability to stimulate diverse oncogenic signaling pathways that lead to neoplastic transformation of fibroblast cell lines and tumorigenesis in nude mice models. Studies from our laboratory as well as others have shown that the growth-promoting activities of Gα(12) and Gα(13) involve potent activation of c-Jun N-terminal kinases (JNKs). Our previous studies have indicated that the JNK-interacting leucine zipper protein (JLP), a scaffold protein involved in the structural and functional organization of the JNK/p38 mitogen-activated protein kinase module, tethers Gα(12) and Gα(13) to the JNK signaling module. In the present study, in addition to demonstrating the physical association between JLP and Gα(12), we show that this interaction is enhanced by the receptor- or mutation-mediated activation of Gα(12). We also establish that JLP interacts with Gα(12) through the C-terminal domain that has been previously identified to be involved in binding to Gα(13). Furthermore, using this C-terminal domain as a competitively inhibitor of JLP that can disrupt Gα(12)-JLP interaction, we demonstrate that JLP is required for the stimulation of JNK by Gα(12). Our results also indicate that such JLP interaction is required for Gα(12) as well as Gα(13)-mediated neoplastic transformation of JLP. These studies demonstrate for the first time a functional role for JLP in the gep oncogene-regulated neoplastic signaling pathway.

Endodermal differentiation of murine embryonic carcinoma cells by retinoic acid requires JLP, a JNK-scaffolding protein.

Retinoic acid (RA) is a morphogen that induces endodermal differentiation of murine P19 embryonic carcinoma cells. RA-induced differentiation of P19 cells has been used as a model system to define the differentiation programs of pluripotent stem cells. Using this system it has been shown that G alpha13--the alpha-subunit of the heterotrimeric G protein G13--and its activation of JNK-module are critically required for the endodermal differentiation of P19 cells. However, the mechanism through which G alpha13 is linked to JNK-module is unknown. Here, we report that RA stimulates the expression of JNK-interacting leucine zipper protein (JLP), a newly identified JNK-scaffolding protein and its critical role in RA-mediated endodermal differentiation. Our results indicate that there is a physical association between JLP and G alpha13 in RA-stimulated P19 cells. More interestingly, silencing JLP abrogates RA-mediated endodermal differentiation of P19 cells analogous to the effects seen with the silencing of G alpha13 or JNK. Therefore, our studies presented here identify for the first time, a novel role for a newly identified scaffolding protein in RA-mediated endodermal differentiation, providing a new signaling conduit to transmit signals from RA to JNK module.

JNK-interacting leucine zipper protein is a novel scaffolding protein in the Galpha13 signaling pathway.

Scaffolding proteins play a critical role in conferring specificity and fidelity to signaling pathways. The JNK-interacting leucine zipper protein (JLP) has been identified as a scaffolding protein involved in linking components of the JNK signaling module. Galpha(12) and Galpha(13), the alpha-subunits of heterotrimeric G proteins G12 and G13, respectively, stimulate the JNK module in diverse cell types. Here, we report that Galpha(13) physically interacts with JLP, and this interaction enhances Galpha(13)-mediated JNK activation. We also demonstrate endogenous interaction between JLP and Galpha(13) in MCF-7 cells. JLP interaction is specific to the G12 family of alpha-subunits via its C-terminal domain (termed GID-JLP), spanning amino acids 1165-1307, and this interaction is more pronounced with the mutationally or functionally activated form of Galpha(13) compared to that of wild-type Galpha(13). The presence of a ternary complex consisting of Galpha(13), JLP, and JNK suggests a role for JLP in tethering Galpha(13) to the signaling components involved in JNK activation. Coexpression of GID-JLP disrupts ternary complex formation in addition to attenuating Galpha(13)-stimulated JNK activity. These findings identify JLP as a novel scaffolding protein in the Galpha(13)-mediated JNK signaling pathway.