Drug Development for Hypertension: Do We Need Another Antihypertensive Agent for Resistant Hypertension?

Soluble Guanylate Cyclase Stimulators and Activators

When Furchgott, Murad, and Ignarro were honored with the Nobel prize for the identification of nitric oxide (NO) in 1998, the therapeutic implications of this discovery could not be fully anticipated. This was due to the fact that available therapeutics like NO donors did not allow a constant and long-lasting cyclic guanylyl monophosphate (cGMP) stimulation and had a narrow therapeutic window. Now, 20 years later, the stimulator of soluble guanylate cyclase (sGC), riociguat, is on the market and is the only drug approved for the treatment of two forms of pulmonary hypertension (PAH/CTEPH), and a variety of other sGC stimulators and sGC activators are in preclinical and clinical development for additional indications. The discovery of sGC stimulators and sGC activators is a milestone in the field of NO/sGC/cGMP pharmacology. The sGC stimulators and sGC activators bind directly to reduced, heme-containing and oxidized, heme-free sGC, respectively, which results in an increase in cGMP production. The action of sGC stimulators at the heme-containing enzyme is independent of NO but is enhanced in the presence of NO whereas the sGC activators interact with the heme-free form of sGC. These highly innovative pharmacological principles of sGC stimulation and activation seem to have a very broad therapeutic potential. Therefore, in both academia and industry, intensive research and development efforts have been undertaken to fully exploit the therapeutic benefit of these new compound classes. Here we summarize the discovery of sGC stimulators and sGC activators and the current developments in both compound classes, including the mode of action, the chemical structures, and the genesis of the terminology and nomenclature. In addition, preclinical studies exploring multiple aspects of their in vitro, ex vivo, and in vivo pharmacology are reviewed, providing an overview of multiple potential applications. Finally, the clinical developments, investigating the treatment potential of these compounds in various diseases like heart failure, diabetic kidney disease, fibrotic diseases, and hypertension, are reported. In summary, sGC stimulators and sGC activators have a unique mode of action with a broad treatment potential in cardiovascular diseases and beyond.

sGC stimulation lowers elevated blood pressure in a new canine model of resistant hypertension

Therapy-resistant hypertension is a serious medical problem, causing end-organ damage, stroke, and heart failure if untreated. Since the standard of care fails in resistant hypertension patients, there is still a substantial unmet medical need for effective therapies. Active stimulation of soluble guanylyl cyclase via novel soluble guanylyl cyclase stimulators might provide an effective treatment option. To test this hypothesis, we established a new experimental dog model and investigated the effects of the soluble guanylyl cyclase-stimulator BAY 41-2272. In beagle dogs, a resistant hypertension phenotype was established by combining unilateral renal wrapping with the occlusion of the renal artery in the contralateral kidney. The most frequently used antihypertensive drugs were administered orally, either alone or in combination, and their acute effect on telemetric measured blood pressure was assessed and compared with that of BAY 41-2272. The chosen disease stimulus led to a moderate and stable increase in blood pressure. Even high doses of standard-of-care antihypertensives only slightly decreased blood pressure. In contrast, the administration of the soluble guanylyl cyclase stimulator BAY 41-2272 as standalone therapy led to a dose-dependent reduction in blood pressure (-14.1 ± 1.8 mmHg). Moreover, BAY 41-2272 could also further decrease blood pressure in addition to a triple combination of standard-of-care antihypertensives (-28.6 ± 13.2 mmHg). BAY 41-2272 was highly efficient as a standalone treatment in resistant hypertension but was also effective in addition to standard-of-care treatment. These data strongly suggest that soluble guanylyl cyclase stimulators might provide an effective pharmacologic therapy for patients with resistant hypertension.

Resistant hypertension: new insights and therapeutic perspectives

Resistant hypertension (RH) is a concept that currently goes beyond the classical definition of blood pressure ≥140/90 mmHg in subjects receiving three or more drugs of different classes at maximally tolerated doses. Here, we review the clinical relevance of RH and the different types of RH-associated phenotypes, namely refractory hypertension, controlled resistant hypertension, and masked uncontrolled hypertension. We also discuss current drug strategies and future treatments for these high-risk phenotypes.

Creatine kinase, energy reserve, and hypertension: from bench to bedside

We hypothesized that human variation in the activity of the ATP regenerating enzyme creatine kinase (CK) activity affects hypertension and cardiovascular disease risk. CK is tightly bound close to ATP-utilizing enzymes including Ca2+-ATPase, myosin ATPase, and Na+/K+-ATPase, where it rapidly regenerates ATP from ADP, H+, and phosphocreatine. Thus, relatively high CK was thought to enhance ATP-demanding processes including resistance artery contractility and sodium retention, and reduce ADP-dependent functions. In a series of studies of our group and others, CK was linked to hypertension and bleeding risk. Plasma CK after rest, used as a surrogate measure for tissue CK, was associated with high blood pressure and failure of antihypertensive therapy in case-control and population studies. Importantly, high tissue CK preceded hypertension in animal models and in humans, and human vascular tissue CK gene expression was strongly associated with clinical blood pressure. In line with this, CK inhibition substantially reduced the contractility of human resistance arteries ex vivo. We also presented evidence that plasma CK reduced ADP-dependent platelet aggregation. In subsequent intervention studies, the oral competitive CK inhibitor beta-guanidinopropionic acid (GPA) reduced blood pressure in spontaneously hypertensive rats (SHRs), and a 1-week trial of sub-therapeutic dose GPA in healthy men was uneventful. Thus, based on theoretical concepts, evidence was gathered in laboratory, case-control, and population studies that high CK is associated with hypertension and with bleeding risk, potentially leading to a new mode of cardiovascular risk reduction with CK inhibition.

The acute effect of beta-guanidinopropionic acid versus creatine or placebo in healthy men (ABC-Trial): A randomized controlled first-in-human trial

Aims

Increasing evidence indicates that the ATP‐generating enzyme creatine kinase (CK) is involved in hypertension. CK rapidly regenerates ATP from creatine phosphate and ADP. Recently, it has been shown that beta‐guanidinopropionic acid (GPA), a kidney‐synthesized creatine analogue and competitive CK inhibitor, reduced blood pressure in spontaneously hypertensive rats. To further develop the substance as a potential blood pressure‐lowering agent, we assessed the tolerability of a sub‐therapeutic GPA dose in healthy men.

Methods

In this active and placebo‐controlled, triple‐blind, single‐centre trial, we recruited 24 healthy men (18–50 years old, BMI 18.5–29.9 kg m⁻²) in the Netherlands. Participants were randomized (1:1:1) to one week daily oral administration of GPA 100 mg, creatine 5 g, or matching placebo. The primary outcome was the tolerability of GPA, in an intent‐to‐treat analysis.

Results

Twenty‐four randomized participants received the allocated intervention and 23 completed the study. One participant in the placebo arm dropped out for personal reasons. GPA was well tolerated, without serious or severe adverse events. No abnormalities were reported with GPA use in clinical safety parameters, including physical examination, laboratory studies, or 12‐Lead ECG. At day 8, mean plasma GPA was 213.88 (SE 0.07) in the GPA arm vs. 32.75 (0.00) nmol l⁻¹ in the placebo arm, a mean difference of 181.13 (95% CI 26.53–335.72).

Conclusion

In this first‐in‐human trial, low‐dose GPA was safe and well‐tolerated when used during 1 week in healthy men. Subsequent studies should focus on human pharmacokinetic and pharmacodynamic assessments with different doses.