Long Term Effectiveness and Safety of Intracavernosal Botulinum Toxin A as an Add-on Therapy to Phosphosdiesterase Type 5 Inhibitors or Prostaglandin E1 Injections for Erectile Dysfunction

Embracing the Versatility of Botulinum Neurotoxins in Conventional and New Therapeutic Applications

Botulinum neurotoxins (BoNTs) have been used for almost half a century in the treatment of excessive muscle contractility. BoNTs are routinely used to treat movement disorders such as cervical dystonia, spastic conditions, blepharospasm, and hyperhidrosis, as well as for cosmetic purposes. In addition to the conventional indications, the use of BoNTs to reduce pain has gained increased recognition, giving rise to an increasing number of indications in disorders associated with chronic pain. Furthermore, BoNT-derived formulations are benefiting a much wider range of patients suffering from overactive bladder, erectile dysfunction, arthropathy, neuropathic pain, and cancer. BoNTs are categorised into seven toxinotypes, two of which are in clinical use, and each toxinotype is divided into multiple subtypes. With the development of bioinformatic tools, new BoNT-like toxins have been identified in non-Clostridial organisms. In addition to the expanding indications of existing formulations, the rich variety of toxinotypes or subtypes in the wild-type BoNTs associated with new BoNT-like toxins expand the BoNT superfamily, forming the basis on which to develop new BoNT-based therapeutics as well as research tools. An overview of the diversity of the BoNT family along with their conventional therapeutic uses is presented in this review followed by the engineering and formulation opportunities opening avenues in therapy.

Safety and Effectiveness of Repeated Botulinum Toxin A Intracavernosal Injections in Men with Erectile Dysfunction Unresponsive to Approved Pharmacological Treatments: Real-World Observational Data

Intracavernosal injections of botulinum toxin A (BTX/A ic) may be effective for difficult-to-treat erectile dysfunction (ED). This is a retrospective case series study of the effectiveness of repeated off-label BTX/A ic (onabotulinumtoxinA 100U, incobotulinumtoxinA 100U or abobotulinumtoxinA 500U) in men with ED and insufficient response to phosphodiesterase type 5 inhibitors (PDE5-Is) or prostaglandinE1 intracavernosal injections (PGE1 ICIs), defined as an International Index of Erectile Function-Erectile Function domain score (IIEF-EF) < 26 on treatment. Further injections were performed on patients' requests, and the files of men who underwent at least two injections were reviewed. The response to BTX/A ic was defined as the achievement of the minimally clinically important difference in IIEF-EF adjusted to the severity of ED on treatment at baseline. Out of 216 men treated with BTX/A ic and PDE5-Is or PGE1-ICIs, 92 (42.6%) requested at least a second injection. The median time since the preceding injection was 8.7 months. In total, 85, 44 and 23 men received, respectively, two, three and four BTX/A ic. The overall response rate was 77.5%: 85.7% in men with mild ED, 79% for moderate ED and 64.3% for severe ED on treatment. The response increased with repeated injections: 67.5%, 87.5% and 94.7%, respectively, after the second, third and fourth injections. Post-injection changes in IIEF-EF were similar across injections. The time from injection to request for a further injection varied little. Four men reported penile pain at the time of injection (1.5% of all injections), and one experienced a burn at the penile crus. Repeated BTX/A injections combined with PDE5-Is or PGE1-ICIs produced an effective and durable response, with acceptable safety.

Conservative Non-surgical Options for Erectile Dysfunction

PURPOSE OF REVIEW

This study aimed to review recent evidence on conservative non-surgical options for erectile dysfunction (ED) in men. A narrative review of the literature was performed. A comprehensive search in the MEDLINE, Embase, and Cochrane databases was done. Papers in English language, published from May 2017 until May 2022, were included. Papers reporting basic research or animal research were excluded, as long as reviews or meta-analyses. Congress reports, clinical cases, or clinical trials protocols with no results were also excluded.

RECENT FINDINGS

We found a multitude of different treatment modalities for ED. We must take into account the type of patient, their comorbidities, the origin of their ED, and its severity in order to reproduce effective results using these therapies. Some of the treatments show good results with a good level of evidence (new IPDE5 formulations, intracavernous injections, shock wave therapy, hormonal theraphy, psycho-sexual theraphy). However, others (some new molecules, stem cell theraphy, platelet-rich plasma injections, oxygenation-based therapy, nutraceuticals), although some of them present promising results, require randomized studies with a larger number of patients and a longer follow-up time to be able to establish firm recommendations. Regarding the conservative treatment of erectile dysfunction, in recent years, some therapies have been consolidated as effective and safe for certain types of patients. On the other hand, other treatment modalities, although promising, still lack the evidence and the necessary follow-up to be recommended in daily practice.

Intracavernosal OnabotulinumtoxinA Exerts a Synergistic Pro-Erectile Effect When Combined With Sildenafil in Spontaneously Hypertensive Rats

BACKGROUND

Botulinum toxin A (BTX-A) has a variety of uses in medicine. Some evidence suggests that intracavernosal (ic) BTX-A injection administered in addition to phosphodiesterase type 5 inhibitors (PDE5-Is) could effectively treat erectile dysfunction (ED) in insufficient responders to PDE5-Is.

AIM

To provide experimental pharmacological evidence for the use of onabotulinumtoxinA ic alone or in combination with PDE5-Is for difficult-to-treat ED. We thus compared the effects of BTX-A ic alone and BTX-A ic combined with PDE5-I iv, and a placebo treatment ic or iv.

METHODS

Erectile function was evaluated following cavernous nerve electrical stimulation (6 V, 1-millisecond pulse, 45-second duration) at different frequencies (0, 2, 3, 4, 5, 7.5, and 10 Hz) in 4 groups (n = 8 / group) of anesthetized, spontaneously hypertensive rats, a robust animal model of ED of vascular origin. Rats were treated by onabotulinumtoxinA 10U or saline ic 1 week prior to erectile function testing and sildenafil (0.3 mg/kg) or saline iv 4 minutes prior to testing. Frequency-response curves were compared with a 2 way ANOVA.

OUTCOMES

Both onabotulinumtoxinA ic, and sildenafil iv significantly improved erectile responses in spontaneously hypertensive rats, however the effect was greatly amplified when the treatments were combined.

RESULTS

Intracavernosal pressure and/or mean arterial pressure ratios were significantly increased by sildenafil and onabotulinumtoxinA ic versus the control condition. OnabotulinumtoxinA 10U ic combined with sildenafil iv significantly potentiated erectile responses. Area under the curve and/or mean arterial pressure ratio increased by 19% with sildenafil iv, by 15% with onabotulinumtoxinA ic and by 58% with the combined treatment following cavernous nerve electrical stimulation at 6V, 1 ms, 10 Hz: these stimulation parameters elicited the maximal erectile response.

CLINICAL TRANSLATION

These data provide a pharmacological rationale for the combined administration of onabotulinumtoxinA ic and sildenafil iv since the effects of both treatments were potentiated when their administration was combined.

STRENGTHS & LIMITATIONS

First evidence of a synergistic pro-erectile effect of BTX-A combined with PDE5-I, however the mechanism behind the pro-erectile effect of BTX-A ic remains hypothetical.

CONCLUSIONS

These results support further studies into the mechanisms behind the pro-erectile effect of BTX-A ic, as well as multicenter randomized control trials to evaluate the safety and efficacy of BTX-A ic combined with sildenafil for difficult-to-treat ED. Giuliano F., Joussain C., Denys P., et al. Intracavernosal OnabotulinumtoxinA Exerts a Synergistic Pro-Erectile Effect When Combined With Sildenafil in Spontaneously Hypertensive Rats. J Sex Med 2022;19:899-906.

Effectiveness and Safety of Intracavernosal IncobotulinumtoxinA (Xeomin®) 100 U as an Add-on Therapy to Standard Pharmacological Treatment for Difficult-to-Treat Erectile Dysfunction: A Case Series

Registered pharmacological treatments are insufficiently effective for erectile dysfunction (ED) in around 30% of affected men. Intracavernosal injection (ICI) of ona- and abobotulinumtoxinA can reduce ED in insufficient responders. We aimed to assess the safety and effectiveness of incobotulinumtoxinA ICI as an add-on therapy to phosphodiesterase-type 5 inhibitors (PDE5-Is) or prostaglandinE1 ICIs (PGE1 ICIs) to treat ED that did not respond sufficiently to this treatment alone. We retrospectively analyzed data from 66 men with difficult to treat ED treated with single or repeated incobotulinumtoxinA 100U ICI as an add-on therapy. Response rate (increase in International Index of Erectile Function-Erectile Function domain score ≥ the minimum clinically important difference) was 52% (median (1st–3rd quartile) 43.5 (34–71) days post-incobotulinumtoxinA ICI). ED etiology (except spinal cord injury) and severity did not influence effectiveness. Only a clinically significant response to the 1st injection predicted a request for a 2nd injection (OR = 5.6, 95%, CI 1.6–19.4). Three men reported mild penile pain during the injection. These results provide preliminary evidence for the effectiveness and safety of incobotulinumtoxinA ICI as an add-on therapy to treat ED that is insufficiently responsive to standard care and provides support for the multicenter randomized clinical trial NCT05196308.