The neurokinin1 receptor antagonist aprepitant as an antiemetic for moderately emetogenic chemotherapy

Aprepitant Has Mixed Effects on Nausea and Reduces Other Symptoms in Patients With Gastroparesis and Related Disorders

BACKGROUND & AIMS

There are few effective treatments for nausea and other symptoms in patients with gastroparesis and related syndromes. We performed a randomized trial of the ability of the neurokinin-1 receptor antagonist aprepitant to reduce symptoms in patients with chronic nausea and vomiting caused by gastroparesis or gastroparesis-like syndrome.

METHODS

We conducted a 4-week multicenter, double-masked trial of 126 patients with at least moderate symptoms of chronic nausea and vomiting of presumed gastric origin for a minimum of 6 months. Patients were randomly assigned to groups given oral aprepitant (125 mg/day, n = 63) or placebo (n = 63). The primary outcome from the intention-to-treat analysis was reduction in nausea, defined as a decrease of 25 mm or more, or absolute level below 25 mm, on a daily patient-reported 0-to-100 visual analog scale (VAS) of nausea severity. We calculated relative risks of nausea improvement using stratified Cochran-Mental-Haenszel analysis.

RESULTS

Aprepitant did not reduce symptoms of nausea, based on the primary outcome measure (46% reduction in the VAS score in the aprepitant group vs 40% reduction in the placebo group; relative risk, 1.2; 95% CI, 0.8-1.7) (P = .43). However, patients in the aprepitant group had significant changes in secondary outcomes such as reduction in symptom severity (measured by the 0-5 Gastroparesis Clinical Symptom Index) for nausea (1.8 vs 1.0; P = .005), vomiting (1.6 vs 0.5; P = .001), and overall symptoms (1.3 vs 0.7; P = .001). Adverse events, predominantly mild or moderate in severity grade, were more common in aprepitant (22 of 63 patients, 35% vs 11 of 63, 17% in the placebo group) (P = .04).

CONCLUSIONS

In a randomized trial of patients with chronic nausea and vomiting caused by gastroparesis or gastroparesis-like syndrome, aprepitant did not reduce the severity of nausea when reduction in VAS score was used as the primary outcome. However, aprepitant had varying effects on secondary outcomes of symptom improvement. These findings support the need to identify appropriate patient outcomes for trials of therapies for gastroparesis, including potential additional trials for aprepitant. ClinicalTrials.gov no: NCT01149369.

Review article: new receptor targets for medical therapy in irritable bowel syndrome

BACKGROUND

Despite setbacks to the approval of new medications for the treatment of irritable bowel syndrome, interim guidelines on endpoints for irritable bowel syndrome (IBS) trials have enhanced interest as new targets for medical therapy are proposed based on novel mechanisms or chemical entities.

AIMS

To review the approved lubiprostone, two targets that are not meeting expectations (tachykinins and corticotrophin-releasing hormone), the efficacy and safety of new 5-HT(4) agonists, intestinal secretagogues (chloride channel activators, and guanylate cyclase-C agonists), bile acid modulation, anti-inflammatory agents and visceral analgesics.

METHODS

Review of selected articles based on PubMed search and clinically relevant information on mechanism of action, safety, pharmacodynamics and efficacy.

RESULTS

The spectrum of peripheral targets of medical therapy addresses chiefly the bowel dysfunction of IBS and these effects are associated with pain relief. The pivotal mechanisms responsible for the abdominal pain or visceral sensation in IBS are unknown. The new 5-HT(4) agonists are more specific than older agents and show cardiovascular safety to date. Secretory agents have high specificity, low bioavailability and high efficacy. The potential risks of agents 'borrowed' from other indications (such as hyperlipidaemia, inflammatory bowel disease or somatic pain) deserve further study.

CONCLUSIONS

There is reason for optimism in medical treatment of IBS with a spectrum of agents to treat bowel dysfunction. However, visceral analgesic treatments are still suboptimal.

Sensory nerves and airway irritability

The lung, like many other organs, is innervated by a variety of sensory nerves and by nerves of the parasympathetic and sympathetic nervous systems that regulate the function of cells within the respiratory tract. Activation of sensory nerves by both mechanical and chemical stimuli elicits a number of defensive reflexes, including cough, altered breathing pattern, and altered autonomic drive, which are important for normal lung homeostasis. However, diseases that afflict the lung are associated with altered reflexes, resulting in a variety of symptoms, including increased cough, dyspnea, airways obstruction, and bronchial hyperresponsiveness. This review summarizes the current knowledge concerning the physiological role of different sensory nerve subtypes that innervate the lung, the factors which lead to their activation, and pharmacological approaches that have been used to interrogate the function of these nerves. This information may potentially facilitate the identification of novel drug targets for the treatment of respiratory disorders such as cough, asthma, and chronic obstructive pulmonary disease.

Characterization of the occurrence of ifosfamide-induced neurotoxicity with concomitant aprepitant

Purpose. Ifosfamide is metabolized by the cytochrome P450 system to its active form, ifosforamide mustard. A potential side effect is neurotoxicity, often manifesting as confusion, hallucination, or seizure. Aprepitant, a neurokinin-1 inhibitor, is recommended for highly and moderately emetogenic chemotherapy regimens and may interfere with the metabolism of ifosfamide as it inhibits CYP3A4. The objective of the study is to identify if an increase in the incidence of neurotoxicity may be associated with the use of aprepitant with concomitant ifosfamide.

Methods. A retrospective study of inpatients with sarcoma who received a two or four-day regimen of MAI (mesna, doxorubicin, and ifosfamide) between January 1, 2004 and December 31, 2006 was conducted. Data collection focused on characterizing neurotoxicity of patients receiving ifosfamide with or without aprepitant. Correlation between serum creatinine, albumin, liver function tests, age, gender, and total doses of ifosfamide was examined.

Results. A total of 45 patients received ifosfamide of which 23 (51%) were male and 24 (53%) received aprepitant. All baseline characteristics were similar for those who received aprepitant versus those who did not. No significant differences were noted between patients with or without neurotoxicity for age, gender, or liver enzymes. Eight patients (18%) of 45 developed neurotoxicity of which six (75%) of those patients also received aprepitant. A trend of increased occurrence of neurotoxicity was noted with aprepitant administration (6 vs. 2 patients respectively, p = 0.176), although a statistical difference was not observed. A relative risk of 2.6 (95% CI, 0.47—26.6) was associated with the addition of aprepitant.

Conclusions. An increased risk was identified for ifosfamide-induced neurotoxicity associated with aprepitant use; however, the observed difference was not statistically significant. The necessity of aprepitant given in association with ifosfamide may need to be reconsidered due to this risk. J Oncol Pharm Practice (2008) 14: 157—162.