Erectile dysfunction (ED) is one of the most common health conditions affecting middle-aged and older men, impacting an estimated 52 percent of men between the ages of 40 and 70 in the US, and globally affecting at least 150 million men. ED is closely linked with numerous comorbidities, including obesity, diabetes, cardiovascular disease, depression, and prior pelvic surgery, as well as lifestyle factors like smoking and alcohol use. Beyond quality-of-life concerns, ED is also an underappreciated cardiovascular risk factor and can signal broader underlying health issues, such as endothelial dysfunction, hormone imbalances, or vascular problems.
Since their introduction nearly 30 years ago, PDE5 (phosphodiesterase type 5) inhibitors — including sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra) — have been the dominant first-line treatment for ED. These drugs act by enhancing the nitric oxide (NO) pathway, which stimulates blood flow into the penis. They have transformed sexual health for many patients, with up to 60 percent achieving erections sufficient for intercourse.
However, approximately 30–35 percent of ED patients fail to respond adequately, particularly those with diabetes, nerve injury following prostate surgery, Peyronie’s disease, or other conditions that impair sexual stimulation, blood flow, or neural signaling. In these cases, the underlying dysfunction disrupts the physiological processes needed to initiate the NO cascade, making PDE5 inhibitors significantly less effective.
Despite the high prevalence of ED and the significant proportion of patients who do not respond to current therapies, there has been little to no innovation in this field over the past 25–30 years. Harin Padma-Nathan, a world leading expert in ED drug development and lead principal investigator on over 110 clinical trials, including those for Viagra and Cialis, told DDN, “It’s amazing — it’s been a quarter of a century, and until recently, there really haven’t been any promising, competitive molecules that could match PDE5 inhibitors in terms of efficacy and tolerability.”
Until now. In a significant advance for ED treatment, Dicot Pharma recently announced research on their drug candidate, LIB-01, which targets an entirely different biological system and could offer a promising alternative for patients who fail to benefit from existing treatments.
A turn toward neurobiology
Padma-Nathan emphasized the need for more effective drug options in the ED space. “In the pivotal trials [of Viagra], the overall response rate was about 70 percent, but in the real world it’s closer to 50 percent.” He added, “There’s room for improvement in efficacy, especially in subpopulations like diabetics or post-nerve sparing radical prostatectomy patients.” Many patients also find the timing and preparation required for PDE5 inhibitors — such as waiting periods, taking them on an empty stomach, or coordinating with infrequent sexual activity — disruptive to intimacy.
Unlike PDE5 inhibitors, which act locally to enhance and trap blood flow in the penis, LIB-01 targets the central nervous system (CNS). Specifically, it modulates the melanocortin system in the brain and spinal cord, a pathway known to play a key role in sexual arousal and erectile function.
The melanocortin system is composed of a family of neuropeptides, including alpha-MSH (alpha-melanocyte-stimulating hormone), which bind to melanocortin receptors (MC1R–MC5R) expressed in various tissues throughout the body. Among these, MC4R is particularly important for regulating sexual behavior, neural signaling related to penile erection, and even aspects of metabolic homeostasis.
Interest in the melanocortin system as a target for sexual dysfunction began more than two decades ago, when early studies showed that systemic administration of Melanotan II (MT-II), a synthetic analog of alpha-MSH, induced erections in multiple species, including humans. This discovery prompted the development of several melanocortinergic agents, such as THIQ (tetrahydroisoquinoline) and bremelanotide (PT-141), both of which demonstrated erectogenic effects thought to arise from activation of melanocortin receptors in the CNS.
Bremelanotide, an MC4R agonist, is the best studied of these and has undergone clinical trials in both men and women. In women, it is FDA-approved for hypoactive sexual desire disorder, a condition defined by low sexual desire that causes significant distress or interpersonal difficulty. Although not approved for ED, in men bremelanotide has demonstrated improved erectile responses and intercourse satisfaction in clinical research. However, side effects such as nausea, along with administration by injection or nasal spray, have limited its appeal compared with current oral treatments.
Padma-Nathan noted, “We originally studied bremelanotide for erectile dysfunction, and it wasn’t particularly remarkable.” He emphasized that while LIB-01 shares some properties with melanocortin receptor agonists, it also possesses unique characteristics, cautioning, “There’s more to the story of LIB-01 than another melanocortin receptor agonist.”
A new generation of melanocortin therapy
Like bremelanotide, LIB-01 targets the MC4R in the brain and spinal cord, modulating central pathways involved in sexual arousal and erectile function. However, preclinical studies show that LIB-01 activates MC4R by increasing the body’s own production of the receptor and its natural agonist, enhancing endogenous signaling.
“One unique feature of this mode of action is the sustained pro-erectile effect,” Elin Trampe, CEO of Dicot Pharma, told DDN. “The impact on gene expression can explain the long-lasting benefits we observed. In the Phase 2a trial, this effect was sustained for eight weeks after just a three-day initial dosing, effectively normalizing sexual function for the couple.”
“It’s quite exciting to see something — even 25 years later — that has the same kind of potential that Viagra had early on. This is a whole paradigm shift in how we think about treating erectile dysfunction,” Padma-Nathan said. “If you can take a pill and still be responding 60 or 90 days later, can patients take drug holidays and still function well? That’s a completely new way of thinking. Even more exciting is the impact of this unique pharmacodynamic in promoting sexual spontaneity.”
Both Trampe and Padma-Nathan also noted that the implications of LIB-01 may extend beyond sexual function. “There are non-sexual aspects — metabolic benefits — that are being characterized now, and that could be the most exciting part of this molecule,” Padma-Nathan said. “Erectile dysfunction is a surrogate marker for cardiovascular health. If you can improve sexual function as part of a larger package of metabolic benefits, that’s a whole new way of looking at treatment. When I saw the data, it was more exciting than what I felt in 1996 when we first started testing Viagra.”
This research could reshape how ED is understood and treated. Rather than viewing ED solely as a vascular issue, emerging evidence highlights a complex neural-endocrine network with untapped therapeutic potential. With millions of men affected worldwide and many cases linked to diabetes, cardiovascular disease, and other health conditions, therapies like LIB-01 may offer not only restored sexual function but also insights into broader aspects of men’s health.
