Erectile dysfunction (ED) is the persistent inability to attain and maintain an erection sufficient to permit satisfactory sexual intercourse. It occurs in 10% to 24% of men, with prevalence increasing with age. The persistent inability to achieve or maintain a satisfactory penile erection has been linked to a range of psychological and biological factors, including age and concurrent medical conditions.
Various risk factors and co-morbidities are associated with ED, including high blood pressure, coronary artery disease, diabetes, benign prostatic hyperplasia, smoking and alcohol consumption. Some common types of medication, including blood pressure drugs, tranquillisers and antidepressants, have also been linked to ED.
ED has a significant impact on the quality of life of sufferers and their partners, and can lead to loss of self-esteem, depression and relationship problems.
ED afflicts a significant proportion of the male population and is age-related. From age 50 upwards, over 25% of men will experience ED, with this figure increasing to 40% in the over-60s and over 60% in those older than 70. The risk of ED is significantly greater in individuals with conditions such as diabetes (50 to 70% of patients with 10 to 15 years earlier onset than in non-diabetics) and high blood pressure (70% ED prevalence). These patients also tend to be more refractory to oral therapy (around 50% fail oral therapy versus less than 20% in non-diabetics or cardiovascular patients).
Increased physician and patient awareness and the availability of the first oral agent (Viagra®) for the condition have resulted in increased numbers of ED patients presenting for treatment. Erectile Dysfunction is also better investigated as, resulting in a deficiency in proper blood flow at an end organ, it is understood to be the first onset of cardiovascular dysfunction.
The combined annualised sales for the two top-selling ED drugs, Viagra® and Cialis® were close to $2.5 billion in 2005.
While ED is most frequently treated with oral phosphodiesterase type 5 (PDE5) inhibitors, these agents are associated with a number of side effects and are potentially hazardous in individuals taking nitrate and other medications and have reduced or low efficacy in certain patient populations, notably diabetics and men recovering from prostate or pelvic surgery. Alternative therapies such as vacuum erection devices or injection of drugs into the penis (intracavernosal therapy) are indicated in these patients. Plethora estimates that there are at least 3 million men in the US alone for whom oral ED treatments are not a viable option.
In 2005, Plethora acquired exclusive North American rights to develop and market Invicorp® (PSD510) from Senetek plc. Invicorp is a non-oral treatment for moderate to severe ED and is specifically targeted at men who either do not respond to oral ED drug treatment or are contraindicated due to other courses of medication.