Review of palonosetron: emerging data distinguishing it as a novel 5-HT(3) receptor antagonist for chemotherapy-induced nausea and vomiting

Know your molecule: pharmacological characterization of drug candidates to enhance efficacy and reduce late-stage attrition

Despite advances in chemical, computational and biological sciences, the rate of attrition of drug candidates in clinical development is still high. A key point in the small-molecule discovery process that could provide opportunities to help address this challenge is the pharmacological characterization of hit and lead compounds, culminating in the selection of a drug candidate. Deeper characterization is increasingly important, because the 'quality' of drug efficacy, at least for G protein-coupled receptors (GPCRs), is now understood to be much more than activation of commonly evaluated pathways such as cAMP signalling, with many more 'efficacies' of ligands that could be harnessed therapeutically. Such characterization is being enabled by novel assays to characterize the complex behaviour of GPCRs, such as biased signalling and allosteric modulation, as well as advances in structural biology, such as cryo-electron microscopy. This article discusses key factors in the assessments of the pharmacology of hit and lead compounds in the context of GPCRs as a target class, highlighting opportunities to identify drug candidates with the potential to address limitations of current therapies and to improve the probability of them succeeding in clinical development.

Allostery: The Good, the Bad, and the Ugly

With the advent of functional screening, more allosteric molecules are being discovered and developed as possible therapeutic entities. Allosteric proteins are unique because of two specific properties: 1) separate binding sites for allosteric modulators and guests and 2) mandatory alteration of receptor conformation upon binding of allosteric modulators. For G protein-coupled receptors, these properties produce many beneficial effects on pharmacologic systems that are described here. Allosteric discovery campaigns also bring with them added considerations that must be addressed for the endeavor to be successful, and these are described herein as well. SIGNIFICANCE STATEMENT: Recent years have seen the increasing presence of allosteric molecules as possible therapeutic drug candidates. The scientific procedures to characterize these are unique and require special techniques, so it is imperative that scientists understand the new concepts involved in allosteric function. This review examines the reasons why allosteric molecules should be considered as new drug entities and the techniques required to optimize the discovery process for allosteric molecules.

The association of adverse reactions and depression in cervical cancer patients treated with radiotherapy and/or chemotherapy: moderated mediation models

Objective

Several studies reported that adverse reactions to treatment, neuroticism, marital relations, and quality of life may impact the development of depression in cervical cancer patients treated with radiotherapy and/or chemotherapy, but the associations between them remained unclear. This study investigated the associations between these factors using moderated mediation models.

Methods

Data were extracted from a survey involving cervical cancer patients treated with radiotherapy and/or chemotherapy at five tertiary hospitals in Hubei Province, China, from June to December 2022. The SPSS-PROCESS program was used to develop a moderated mediation model to study the roles of neuroticism, quality of life, and marital relations in the association between adverse reactions and depression in the study population.

Results

A total of 802 cervical cancer patients treated with radiotherapy and/or chemotherapy (54.84 ± 9.68 years) were recruited. The prevalence of depression among these patients was 72.72%, with four symptom clusters of dizziness-ringing in the ears, digestive system-related symptoms, skin dryness and itching, and urinary frequency-urgency-leakage. Adverse reactions directly and positively affected the occurrence of depression, neuroticism mediated the association between adverse reactions and depression, while this association varied according to the quality of life and marital relations.

Conclusion

Our findings suggest that depression is common among cervical cancer patients receiving radiotherapy and/or chemotherapy. Intervention targets for depression in cervical cancer patients should be precisely selected and targeted according to the quality of life and marital relations differences in patients, taking into account the cost of the intervention and the benefit to the patient.

Allosteric Antagonism of the Pregnane X Receptor (PXR): Current-State-of-the-Art and Prediction of Novel Allosteric Sites

The pregnane X receptor (PXR, NR1I2) is a xenobiotic-activated transcription factor with high levels of expression in the liver. It not only plays a key role in drug metabolism and elimination, but also promotes tumor growth, drug resistance, and metabolic diseases. It has been proposed as a therapeutic target for type II diabetes, metabolic syndrome, and inflammatory bowel disease, and PXR antagonists have recently been considered as a therapy for colon cancer. There are currently no PXR antagonists that can be used in a clinical setting. Nevertheless, due to the large and complex ligand-binding pocket (LBP) of the PXR, it is challenging to discover PXR antagonists at the orthosteric site. Alternative ligand binding sites of the PXR have also been proposed and are currently being studied. Recently, the AF-2 allosteric binding site of the PXR has been identified, with several compounds modulating the site discovered. Herein, we aimed to summarize our current knowledge of allosteric modulation of the PXR as well as our attempt to unlock novel allosteric sites. We describe the novel binding function 3 (BF-3) site of PXR, which is also common for other nuclear receptors. In addition, we also mention a novel allosteric site III based on in silico prediction. The identified allosteric sites of the PXR provide new insights into the development of safe and efficient allosteric modulators of the PXR receptor. We therefore propose that novel PXR allosteric sites might be promising targets for treating chronic metabolic diseases and some cancers.

Development of 3-(4-Chlorophenyl)-1-(phenethyl)urea Analogues as Allosteric Modulators of the Cannabinoid Type-1 Receptor: RTICBM-189 is Brain Penetrant and Attenuates Reinstatement of Cocaine-Seeking Behavior

We have shown that CB₁ receptor negative allosteric modulators (NAMs) attenuated the reinstatement of cocaine-seeking behaviors in rats. In an effort to further define the structure-activity relationships and assess the druglike properties of the 3-(4-chlorophenyl)-1-(phenethyl)urea-based CB₁ NAMs that we recently reported, we introduced substituents of different electronic properties and sizes to the phenethyl group and evaluated their potency in CB₁ calcium mobilization, cAMP, and GTPγS assays. We found that 3-position substitutions such as Cl, F, and Me afforded enhanced CB₁ potency, whereas 4-position analogues were generally less potent. The 3-chloro analogue (31, RTICBM-189) showed no activity at >50 protein targets and excellent brain permeation but relatively low metabolic stability in rat liver microsomes. Pharmacokinetic studies in rats confirmed the excellent brain exposure of 31 with a brain/plasma ratio K_p of 2.0. Importantly, intraperitoneal administration of 31 significantly and selectively attenuated the reinstatement of the cocaine-seeking behavior in rats without affecting locomotion.

G-Protein/Receptor inhibitors as blockers of receptor signaling

This paper describes the behavior of binding and functional receptor systems where an antagonist of the receptor/G protein binding reaction is added as a blocker of agonist-induced receptor function. For agonist radioligands, the reduction of G protein receptor interaction leads to a possible change in the binding affinity of the agonist radioligand to the receptor. Reciprocally, the allosteric cooperativity between the agonist and the G protein binding site antagonist (quantified by the factor γ_B) affects the potency of the G protein antagonist modulator; this model presents the various profiles that would be expected for modulators that reduce (γ_B = 0.01), have no effect on (γ_B = 1) and increase (γ_B = 100) the affinity of the agonist for the receptor. It will be seen that modulators that increase the affinity of the receptor for the agonist are the most potent antagonists and may attain a profile of some special negative allosteric modulators referred to as PAM antagonists. In all cases, these modulators will be inverse agonists of constitutive receptor activity. This model presents a strategy for the discovery of PAM antagonists for therapeutic blockade of physiological signaling.

Analytical Pharmacology: How Numbers Can Guide Drug Discovery

The unique ways in which pharmacological data compares to mathematical models are described. Examples show that insights into agonist action (prediction of agonism in vivo) and antagonist mechanism of action (orthosteric vs allosteric) can be gained that assist in the candidate selection process for new drugs in drug discovery and development efforts. In addition, the impact of component processes on complex physiological systems can be delineated, such as the effects of the hepatic system on whole body clearance in pharmacokinetics and prediction of drug-drug interactions. Finally, models are instrumental in the procurement of universal drug parameters that can be used in medicinal chemistry-based structure-activity relationships. The revitalization of these ideas under the banner of "Analytical Pharmacology" may serve to re-emphasize these concepts over qualitative description and lead to a better foundation for drug discovery.

Role of rational diet in postoperative treatment of gastric cancer and application prospect of traditional Chinese medicine diet

The toxic side effects of postoperative radiotherapy and chemotherapy in gastric cancer (GC) often cause patients to have cancer cachexia and poor quality of life. Dietary adjuvant therapy can significantly promote GC patients to recover the body function, alleviate inflammation, improve anticancer treatment tolerance, improve postoperative quality of life and prolong survival. Given the advantages of diet in the postoperative treatment of GC, this paper discusses the role of modern medicine's elemental nutrition diet and traditional Chinese medicine diet in the postoperative treatment of GC, which can help clinicians better understand traditional Chinese medicine treatment in relieving the overall dysfunction of the body. Furthermore, the combination of traditional Chinese medicine diet with the modern medical nutrition diet evaluation system can expand the use of traditional Chinese medicine diet in the clinical treatment of GC.

PAM-Antagonists: A Better Way to Block Pathological Receptor Signaling?

Seven transmembrane receptor (7TMR) responses are modulated by orthosteric and allosteric ligands to great therapeutic advantage. Here we introduce a unique class of negative allosteric modulator (NAM) - the positive allosteric modulator (PAM)-antagonist - that increases the affinity of the receptor for the agonist but concomitantly decreases agonist efficacy when cobound. Notably, the reciprocation of allosteric energy causes the orthosteric agonist to increase the affinity of the receptor for the PAM-antagonist; thus, this modulator seeks out and destroys agonist-bound receptor complexes. When contrasted with standard orthosteric and allosteric antagonists it is clear that PAM-antagonists are uniquely well suited to reversing ongoing persistent agonism and provide favorable target coverage in vivo. Specifically, the therapeutic application of PAM-antagonists to reverse pathological overactivation (e.g., endothelin vasoconstriction) is emphasized.

Comparative investigation of the anti-emetic effects of granisetron and palonosetron during the treatment of acute myeloid leukemia

Chemotherapy-induced nausea and vomiting has a considerable negative impact on the quality of life of patients with cancer. Unfortunately, there has been little progress in the development of supportive therapies for the anti-emetic treatment of patients with hematopoietic tumors. This lack of supportive treatments motivated the present retrospective comparison between two groups of anti-emetic drugs. The current study aimed to compare granisetron and palonosetron in order to determine which is more effective, based on cases of patients undergoing remission induction therapy and consolidation therapy for the treatment of acute myeloid leukemia. Granisetron or palonosetron were administered in Japanese-approved dosages (3 mg granisetron once per day for 5 or 7 days, or one administration of 0.75 mg palonosetron). Patients were randomly selected, and their clinical information was acquired from medical records. The data represent the doctors' and nurses' records. The results demonstrated that palonosetron treatment (in which the drug was administered alone or in combination with aprepitant) was more effective than granisetron treatment for the complete control of acute vomiting. Therefore, in the treatment of hematopoietic malignancies, palonosetron is an effective regimen to be administered alongside more than 5 continuous days of anti-cancer agents. Furthermore, the combination of palonosetron and aprepitant was found to be the optimal combination. In conclusion, palonosetron is superior to granisetron for the prevention of nausea and vomiting induced by chemotherapy for hematological cancers. In Japan, the standard dose of palonosetron is 0.75 mg; a dose of 0.25 mg of palonosetron must be compared with 0.75 mg in future studies.

Evaluation of an every-other-day palonosetron schedule to control emesis in multiple-day high-dose chemotherapy

AIM

Efficacy of intermittent palonosetron dosing in patients undergoing multiple-day, high-dose chemotherapy (HDC) was investigated.

PATIENTS & METHODS

Fifty-eight patients received palonosetron (0.25 mg intravenous [iv.]) every other day plus daily dexamethasone (8 mg iv. twice daily) dosing. The primary end point was complete control (CC; no emesis, no rescue anti-emetics, and no more than mild nausea) in the overall acute-period (until 24 h after chemotherapy completion).

RESULTS

Acute-period CC occurred in 81% and 50% of patients receiving palonosetron and ondansetron (historical control cohort), respectively. Palonosetron (odds ratio [OR]: 4.37; p = 0.001) and a longer duration of HDC regimen (OR: 3.47; p = 0.011) independently predicted a better anti-emetic outcome.

CONCLUSION

Palonosetron every other day plus daily dexamethasone is an effective anti-emetic coverage in patients undergoing HDC.

Intravenous palonosetron increases the incidence of QTc prolongation during sevoflurane general anesthesia for laparotomy

Background

Palonosetron is a recently introduced 5-hydroxytryptamine-3 (5-HT₃) receptor antagonist useful for postoperative nausea and vomiting prophylaxis. However, 5-HT₃ receptor antagonists increase the corrected QT (QTc) interval in patients who undergo general anesthesia. This retrospective study was performed to evaluate whether palonosetron would induce a QTc prolongation in patients undergoing general anesthesia with sevoflurane.

Methods

We reviewed a database of 81 patients who underwent general anesthesia with sevoflurane. We divided the records into palonosetron (n = 41) and control (n = 40) groups according to the use of intraoperative palonosetron, and analyzed the electrocardiographic data before anesthesia and 30, 60, 90, and 120 min after skin incision. Changes in the QTc interval from baseline, mean blood pressure, heart rate, body temperature, and sevoflurane concentrations at each time point were compared between the two groups.

Results

The QTc intervals at skin incision, and 30, 60, 90, and 120 min after the skin incision during general anesthesia were significantly longer than those at baseline in the two groups (P < 0.001). The changes in the QTc intervals were not different between the two groups (P = 0.41). However, six patients in the palonosetron group showed a QTc interval > 500 ms 30 min after skin incision, whereas no patient did in the control group (P = 0.01). No significant differences were observed between the two groups in mean blood pressure, body temperature, heart rate, or sevoflurane concentrations.

Conclusions

Palonosetron may induce QTc prolongation during the early general anesthesia period with sevoflurane.

Optimizing treatment outcomes in patients at risk for chemotherapy-induced nausea and vomiting

Prevention of chemotherapy-induced nausea and vomiting (CINV) is crucial in maximizing patients' quality of life and optimizing outcomes of cancer therapy, and can be done more effectively than ever before. Appropriate antiemetic therapy combined with targeted patient education, clear communication, and management of patient expectations results in optimal emetogenic control. Oncology nurses play a critical role in the prevention and management of CINV. This column reviews the history and pathophysiology of treatments for CINV, as well as patient- and chemotherapy-specific risk factors that should be considered to optimize treatment outcomes in patients with CINV.

Palonosetron: An Evidence-Based Choice in Prevention of Nausea and Vomiting Induced by Moderately Emetogenic Chemotherapy

Aims and background

In 2003, the second-generation, 5-HT3 receptor antagonist (5-HT3 RA) palonosetron was approved by the FDA for the prevention of nausea and vomiting associated with highly and moderately emetogenic chemotherapy. We reviewed the current knowledge on the role of palonosetron against acute and delayed emesis in patients with solid tumors undergoing single-day moderately emetogenic chemotherapy regimens.

Methods

A literature review in PubMed was performed to update currently available preclinical and clinical evidence on palonosetron, prioritizing randomized clinical trials.

Results

The distinct pharmacology of palonosetron provides a rationale behind the improved efficacy observed with the drug in prevention of delayed symptoms. This may be explained by allosteric binding properties and by palonosetron-triggered receptor internalization, which result in prolonged inhibition of the 5-HT3 receptor function. Very recent pharmacology experiments have also suggested that palonosetron would be able to differentially inhibit 5-HT3/neurokinin 1 (NK-1) receptor signaling cross-talk. In two recent meta-analyses, palonosetron was shown to be more effective than other available 5-HT3 RAs in preventing acute and delayed nausea and vomiting for both HEC and MEC. Recent findings also suggest that a single-day regimen of palonosetron plus dexamethasone (both drugs administered intravenously) may provide a reasonable therapeutic alternative to reduce the total dexamethasone dose administered in patients undergoing moderately emetogenic chemotherapy.

Conclusions

On the basis of accumulating data, the evidence-based international guidelines devised from the major organizations have been recently updated to recommend the use of palonosetron plus 3-day dexamethasone for the optimal prevention of nausea and vomiting due to moderately emetogenic chemotherapy. There is still a need to investigate the efficacy of palonosetron in combination with an NK-1 receptor antagonist and dexamethasone in well-designed randomized trials.

Antiemetic efficacy of single-dose palonosetron and dexamethasone in patients receiving multiple cycles of multiple day-based chemotherapy

Introduction

The goal of pharmacological prophylaxis of chemotherapy-induced nausea and vomiting (CINV) should be the elimination of both nausea and vomiting symptoms during all planned chemotherapy cycles. The aim of this study was to assess the efficacy of a single dose of palonosetron and dexamethasone to prevent CINV and to guarantee an adequate food intake (FI) in patients receiving several cycles of multiple day-based chemotherapy (MD-CT).

Methods

Patients with advanced cancer but without a compromised nutritional status (bone mass index ≥ 18.5) were treated with 0.25 mg palonosetron plus 20 mg dexamethasone before MD-CT. The MD-CT regimen was either epirubicin plus ifosfamide or paclitaxel plus cisplatin and ifosfamide. Nausea, vomiting, and FI were monitored in a 7-day diary. Complete response (CR: no vomiting and no rescue therapy) was the primary endpoint, while complete control (CC: CR and no more than mild nausea) and the evaluation of FI were secondary endpoints. The endpoints were evaluated during the overall timescale (0–168 h) of the chemotherapy regimen.

Results

Fifty patients were enrolled, 80% of whom achieved CR and 78% achieved CC. During the six chemotherapy cycles, CR and CC ranged from 76% to 88% and from 62% to 88%, respectively. Moreover, patients with CR had a significantly (p < 0.0001) higher weekly food intake compared with patients not achieving CR.

Conclusions

This trial was the first to assess the efficacy of palonosetron and dexamethasone for the prevention of both nausea and vomiting in patients receiving multiple cycles of MD-CT. In this trial, the ability of patients to intake an adequate amount of food each week was correlated with nausea, thus providing clinicians with an objective parameter for the measurement of the effects of nausea. A single dose of palonosetron and dexamethasone was able to prevent CINV in most patients receiving 3 days of chemotherapy during all planned chemotherapy cycles.

Impact of initiating antiemetic prophylaxis with palonosetron versus ondansetron on risk of uncontrolled chemotherapy-induced nausea and vomiting in patients with lung cancer receiving multi-day chemotherapy

PURPOSE

The purpose of this study is to examine the risk of uncontrolled chemotherapy-induced nausea/vomiting (CINV) among lung cancer patients receiving multi-day chemotherapy and ondansetron- or palonosetron-initiated prophylactic antiemetic regimens in a community oncology setting.

METHODS

The Georgia Cancer Specialists electronic medical records database was used to retrospectively identify lung cancer patients who received multi-day cisplatin or carboplatin regimens with ondansetron or palonosetron on day 1 between April 1, 2006 and July 31, 2009. Uncontrolled CINV events were identified through ICD-9-CM codes (nausea/vomiting), CPT codes (dehydration), rescue medications, nausea/vomiting hospitalizations, and/or antiemetic therapy after last chemotherapy administration of the cycle. Risk for uncontrolled CINV, up to 7 days after last chemotherapy administration, was analyzed at cycle level using logistic regression with regressors of gender, age, number of chemotherapy administration days, Charlson comorbidity index, cancer type, multicancer diagnoses, and chemotherapy regimen.

RESULTS

A total of 209 palonosetron and 153 ondansetron patients (702 and 515 cycles, respectively) met the inclusion criteria. Palonosetron patients were significantly older (mean 67.9 versus 63.9 years; P < 0.0001), with no significant difference in gender, baseline comorbidity score, or multicancer diagnosis. Palonosetron cycles had 63% lower risk for uncontrolled CINV events versus ondansetron cycles [odds ratio (OR) 0.37; 95% confidence interval (CI) 0.25-0.54; P < 0.0001]. Sub-analysis by chemotherapy supported overall analysis (cisplatin OR 0.09; 95% CI 0.04-0.25; P < 0.0001; carboplatin OR 0.46; 95% CI 0.30-0.70; P = 0.0003).

CONCLUSION

In this retrospective analysis of lung cancer patients, multi-day chemotherapy cycles administered with palonosetron on day 1 were associated with a significantly lower risk for uncontrolled CINV events versus ondansetron-initiated chemotherapy cycles.