Captopril, an Angiotensin-Converting Enzyme Inhibitor, Promotes Growth of Immunogenic Tumors in Mice

PURPOSE

Antitumor potential of angiotensin-converting enzyme inhibitors has been shown in different preclinical settings, which always involved immunocompromised organisms or nonimmunogenic tumor models. In our study, we wanted to evaluate the effect of captopril on growth of immunogenic tumors in immunocompetent animals.

EXPERIMENTAL DESIGN

We used different murine tumor models to evaluate the effect of captopril on tumor take and survival of tumor-bearing immunocompetent and immunocompromised mice. We used an orthotopic renal cell cancer model and highly immunogenic tumor model, which were based on kidney subcapsular injection of RenCa cells or s.c. injection of MethA cells, respectively. To show the influence of captopril on antigen-specific immune responses, we have used two model antigens (green fluorescent protein and beta-galactosidase).

RESULTS

Captopril decreased survival of RenCa-bearing, immunocompetent mice in a dose-dependent manner and in adjuvant setting. In nephrectomized mice, captopril shortened their survival. Captopril promoted formation of immunogenic MethA sarcoma tumors but had no effect on nonimmunogenic melanoma cells (B78-H1). Treatment of immunocompromised mice bearing MethA tumors or RenCa kidney tumors with captopril did not affect tumor formation nor survival, respectively. Captopril-treated mice immunized with AdLacZ or AdGFP vectors did not generate or generated decreased numbers of antigen-specific CD8+ T cells, respectively. However, they showed B-cell responses represented by infiltration of MethA tumors with activated B cells and dramatically increased serum level of beta-galactosidase-specific antibodies.

CONCLUSIONS

Our results show a novel role of captopril in tumor biology and the tumor-promoting properties of captopril seem to be associated with its immunomodulatory potential.

Inhibition of the acute effects of angiotensin II by the receptor antagonist irbesartan in normotensive men

Irbesartan (SR 47436, BMS 186295) is an imidazole derivative that specifically binds to the angiotensin type 1 receptor. The purpose of this study was to assess the inhibitory effect of irbesartan on the pressor action of exogenous angiotensin II in healthy subjects, to evaluate the dose dependency and duration of this inhibition, and to determine the effect of irbesartan on plasma components of the renin-angiotensin system. Forty-two healthy male volunteers maintained on ad libitum sodium intake were enrolled in a randomized, double-blind, placebo-controlled, parallel-design, dose-ranging study. On 2 study days 1 week apart, volunteers were given either a placebo or the active drug at one of the chosen doses (5, 25, 50, 75, 100, 150, or 300 mg). The pressor effects of an individually titrated test dose of exogenous angiotensin II as well as plasma levels of angiotensin II, active renin, aldosterone, and treatment drug were determined before and throughout the 24 h after drug administration. The inhibitory effect of irbesartan on the pressor response to angiotensin II was observed within 1 h after dosing, peaked between 2 and 4 h, and lasted more than 24 h for doses of 25 mg and more. The effect was clearly dose related. Two and 24 h after administration of irbesartan, 300 mg, the response of arterial blood pressure (systolic and diastolic) to a given dose of angiotensin II was reduced by approximately 100% and 60%, respectively. Plasma concentrations of angiotensin II and active renin increased markedly after irbesartan administration, whereas plasma concentrations of aldosterone decreased. No evidence was found that the high levels of circulating angiotensin II observed after irbesartan administration could override the inhibitory effect of irbesartan on any of the measured parameters up to 24 h after dose. In conclusion, irbesartan appears to be a well-tolerated, orally active, potent antagonist of the renin-angiotensin system in men.

The efficacy and tolerance of one or two daily doses of eprosartan in essential hypertension. The Eprosartan Multinational Study Group

OBJECTIVE

The primary objective of this double-blind, parallel-group, placebo-controlled, multicentre study was to compare the antihypertensive efficacy of one versus two daily doses of eprosartan, a novel nonbiphenyl, nontetrazole angiotensin II receptor antagonist, in 243 patients with mild to moderate hypertension (sitting diastolic blood pressure > or = 95 to < or = 114 mmHg).

PATIENTS AND METHODS

The patients were randomized to titrated doses of eprosartan at 400-800 mg once a day, eprosartan at 200-400 mg twice a day, or placebo, with the incremental dose titrated over a 9-week period. Patients reaching target blood pressure (sitting diastolic blood pressure of < or = 90 mmHg) continued the fixed-dose treatment for 4 weeks. The primary efficacy measure was the mean change in trough sitting diastolic blood pressure from baseline to the study endpoint, determined on an intent-to-treat basis.

RESULTS

By the end of the study, eprosartan had significantly reduced mean trough sitting systolic and diastolic blood pressure relative to baseline and to placebo. The mean +/- SD change from baseline in diastolic pressure was -9 +/- 8.4 mmHg for the single daily dose, -9 +/- 8.5 mmHg for two doses a day and -4 +/- 8.1 mmHg for placebo (P < 0.0001 versus placebo for both eprosartan regimens). Similarly, both eprosartan regimens significantly reduced mean trough standing systolic and diastolic blood pressure. At the end of the study, the response rate in the single daily dose group (46.8%) was significantly higher than in the placebo group (25.6%). There were no significant differences between the treatment groups in the number of patients whose blood pressure responded to treatment; 41.7% of those taking eprosartan once a day and 44.4% of those taking eprosartan twice a day, and who responded to treatment, were maintained on their original starting doses. The total daily dose required to achieve target blood pressure was comparable, whether eprosartan was administered once or twice a day. Both eprosartan regimens were well tolerated and the incidence of adverse events with eprosartan was similar to that of placebo.

CONCLUSIONS

These results demonstrate that there was no significant difference in antihypertensive efficacy or tolerance between eprosartan taken in one or in two daily doses. Both dosing regimens provided significant and clinically meaningful reductions in blood pressure that were superior to placebo. Eprosartan in a single daily dose was shown to be an effective antihypertensive agent. Because of the good adverse-effect profile and the simplicity of a single daily dose, eprosartan has the potential to improve patient compliance.

Quality of life and calcium channel blockade with nifedipine GITS versus amlodipine in hypertensive patients in Spain. Gastrointestinal Therapeutic System

OBJECTIVE

Compliance with hypertension treatment is affected by treatment-related factors (complexity, side effects), efficacy and compound-specific effects that impact on quality of life. This study examined the differences in quality of life produced by two once-daily calcium channel blockers using different delivery systems: nifedipine gastrointestinal therapeutic system (GITS) and amlodipine.

DESIGN

This was a double-blind, double-dummy, randomized clinical trial comparing nifedipine GITS (30 mg) and amlodipine (5 mg) for 24 weeks following a placebo run-in. Clinical, laboratory evaluations and quality-of-life data were assessed at screening, baseline randomization and three times during active therapy.

SETTING

The study was conducted in 13 medical clinics in Spain.

PATIENTS

The sample comprised 430 screened and 356 randomized patients with mild to moderate hypertension (diastolic blood pressure 95-114 mmHg).

MAIN OUTCOME MEASURES

Change in systolic and diastolic blood pressure and in health-related quality of life were the main outcome measures.

RESULTS

There were no significant differences between active treatment groups in the blood pressure changes (systolic blood pressure: nifedipine GITS -15.5 mmHg; amlodipine -15.7 mmHg). Spontaneous adverse events consistent with calcium channel blockage were not different. The nifedipine GITS group improved in all quality-of-life measures except Sexual Symptom Distress and showed a significantly greater improvement than amlodipine in overall Quality of Life (P< 0.05), General Perceived Health (P < 0.026) and its subscale Vitality (P < 0.019). The amlodipine group declined in overall Quality of Life, General Perceived Health, Vitality and Sleep Disturbance, and significantly in Sexual Symptom Distress (P < 0.045). However, this group improved in self-reported Cognitive Functioning (P=0.036), Mental Acuity (P < 0.005) and Detachment/disorientation (P=0.01).

CONCLUSIONS

These results suggest compound-specific effects on quality of life that may be due to differences in the delivery system. Nifedipine GITS is short-acting (2 h half-life) and is delivered continuously over a 24 h period, while amlodipine has a half-life of 40 h, which may produce more sustained low-level effects. While a more beneficial profile was observed for nifedipine, amlodipine demonstrated potential positive effects on cognitive functioning.

Delapril slows the progression of atherosclerosis and maintains endothelial function in cholesterol-fed rabbits

The renin-angiotensin system is an important modulator of arterial blood pressure and inhibitors of the angiotensin-converting enzyme (ACE-Is) and are currently used in the treatment of hypertension. The pleiotropic actions exerted by angiotensin II (AngII) on the functionality of the vessel wall may have pro-atherosclerotic outcomes; evidence for an anti-atherosclerotic effect of ACE-Is has been presented and an antioxidant effect has been attributed to thiol-containing ACE-Is, like Captopril. The present study has been undertaken to investigate the effect of Delapril, a lipophilic ACE-I, on the development of atherosclerosis in cholesterol-fed rabbits. While it did not correct hyperlipidemia, Delapril dose dependently inhibited the development of atherosclerosis, expressed as aortic area covered by lesions (23.3+/-4.1, 21.3+/-2.4 and 18.5+/-3.3% with Delapril at the daily dose of 5, 10 and 20 mg/kg, respectively, versus 38.2%+/-6.4 for control animals) and its effect was similar to that of Captopril (14.5+/-5.1% at the daily dose of 25 mg/kg). Furthermore, Delapril partially and dose dependently restored endothelium-dependent relaxation, which is impaired in vessels from hypercholesterolemic animals (51.80+/-12.18, 59.74+/-5.16, 69.13+/-8.70 maximal percent relaxation versus 48.26+/-3.05% for the untreated control and 67.67+/-6.72% for Captopril-treated animals). An antioxidant mechanism is unlikely to explain this data, since Delapril does not contain thiol groups. These observations suggest that Delapril may represent an effective pharmacological approach for the treatment of atherosclerosis during its early phases.

An open-label, noncomparative, multicenter study of ramipril in the treatment of patients with mild-to-moderate hypertension

Ramipril, a once-a-day angiotensin-converting enzyme inhibitor, was studied in the treatment of mild-to-moderate hypertension in 240 patients. A total of 194 patients (111 women and 83 men; mean +/- SD age, 46.0 +/- 11.5 years) were considered assessable for study. After a 2-week placebo washout phase, all patients received ramipril 2.5 mg once daily for 4 weeks. At 4 weeks, blood pressure was evaluated for response to therapy. Responders to 2.5 mg were continued on the same dose; nonresponders received 5 mg once daily for another 4 weeks. Results showed that 91% of patients responded after 8 weeks of therapy, 60% to 2.5 mg and 31% to 5 mg. Ramipril was well tolerated and, because of its long half-life, can be considered a true once-a-day angiotensin-converting enzyme inhibitor for the treatment of patients with mild-to-moderate hypertension.