Collagenase Clostridium Histolyticum (Xiaflex) for Peyronie's Disease: What the Evidence Actually Shows

What Is Peyronie's Disease and Who Qualifies for Xiaflex?

Peyronie's disease is a fibrotic connective tissue condition in which collagen plaques form within the tunica albuginea of the penis, causing curvature, pain, and in many cases the inability to have penetrative sex. Prevalence estimates range from 3% to 9% of adult men, though autopsy and imaging data suggest the true figure may be closer to 13% 1. The condition is not simply cosmetic. The 2015 AUA Guideline on Peyronie's Disease states: "Peyronie's disease can cause significant psychological distress, relationship disruption, and sexual dysfunction" 2.

CCH (Xiaflex, Endo Pharmaceuticals) received FDA approval in December 2013 specifically for adult men who have a palpable plaque and a curvature deformity of 30 degrees or more at the start of treatment 3. Men with ventral (downward-toward-urethra) curvature were excluded from the key trials and the approved label does not cover that anatomy. Stable disease is not required; the drug may be used in both the active (acute) and chronic phases, though most clinical protocols prefer to wait at least 12 months from symptom onset before injecting.

Candidates must have a curvature that physically prevents intercourse or causes measurable distress. Men with a curvature below 30 degrees, hourglass deformity without curvature, or hinge deformity alone may not be ideal candidates 4.

How CCH Works: The Mechanism Behind Collagen Dissolution

Collagenase clostridium histolyticum is a mixture of two bacterial collagenase enzymes (AUX-I and AUX-II) derived from Clostridium histolyticum. Injected directly into the plaque, these enzymes cleave the peptide bonds in type I and type III collagen, the predominant collagen subtypes in Peyronie's plaques 5. This enzymatic degradation physically disrupts the structural integrity of the plaque without removing penile tissue.

The process requires mechanical augmentation. After each injection pair, the treating urologist performs a penile modeling procedure approximately 24 to 72 hours after the second injection. Modeling applies controlled lateral force to the erect or semi-erect penis to break apart the enzymatically weakened plaque. The combination of enzymatic action and mechanical force produces greater curvature reduction than either approach alone, a finding supported by the IMPRESS trial design 6.

Each treatment cycle consists of the following sequence: injection 1 on day 1, injection 2 between day 2 and day 4, and office-based modeling 1 to 3 days after injection 2. Patients also perform at-home penile stretching exercises 3 times daily for 6 weeks after modeling. Up to four such cycles are permitted, spaced approximately 6 weeks apart 3.

IMPRESS I and II: The Key Trial Data You Should Know

The IMPRESS (Investigation for Maximal Peyronie's Reduction Efficacy and Safety Studies) I and II trials were Phase III, randomized, double-blind, placebo-controlled studies. Combined, they enrolled 832 men with stable Peyronie's disease (curvature 30, 90 degrees) and followed them through up to 4 treatment cycles 6.

Key efficacy outcomes from the combined analysis:

• Mean change in curvature: CCH group improved by 17.0 degrees (approximately 34% reduction from baseline mean of 49.4 degrees) versus 9.3 degrees in the placebo group (P<0.001) 6.
• Peyronie's Disease Questionnaire (PDQ) bother domain: CCH produced a statistically significant improvement of 2.8 points versus 1.8 points with placebo (P<0.001) 6.
• Clinically meaningful response (defined as curvature reduction ≥20%): achieved in approximately 36% of CCH-treated men versus about 21% in the placebo group 7.

The trials did not show a statistically significant improvement in sexual function scores on the IIEF (International Index of Erectile Function) compared with placebo, suggesting that CCH alone does not reliably rescue erectile function even when curvature is reduced 6.

A useful clinical framework for interpreting these numbers: a 17-degree mean improvement sounds modest, but for a man presenting with 50-degree dorsal curvature, dropping to roughly 33 degrees can restore the ability to have penetrative intercourse. The AUA guideline acknowledges this, noting that "a clinically meaningful improvement may differ from a statistically significant one in individual patients" 2.

Safety Profile and Serious Adverse Events

CCH carries real risks that require informed consent and an experienced injector. The most common adverse events in IMPRESS were injection-site related: penile hematoma (65.6% of CCH subjects), swelling (55%), and pain (46%) 6. Most resolved without intervention. Ecchymosis (bruising) extending to the scrotum or pubic area is common and expected.

Serious adverse events occurred in a small but non-negligible fraction of men. Penile fracture (corporal rupture) was reported in 5 of 551 CCH-treated men (0.9%) across the IMPRESS trials 6. Severe penile hematoma requiring intervention occurred in approximately 0.7% 8. Both events require immediate urological evaluation and potentially surgical repair.

The FDA prescribing information carries a boxed warning for corporal rupture and severe penile hematoma, and requires that Xiaflex be prescribed through a Risk Evaluation and Mitigation Strategy (REMS) program 3. Only certified urologists who have completed the Xiaflex REMS training may administer the drug.

Patients must avoid sexual activity, aggressive penile manipulation, and stretching exercises for at least 2 weeks following each injection pair. Erections should be minimized during this healing window, which sometimes prompts physicians to prescribe a short course of a PDE5 inhibitor at the lowest effective dose to manage nocturnal erections, though this is off-label use 9.

The Role of PDE5 Inhibitors in Peyronie's Disease Management

Erectile dysfunction and Peyronie's disease are intertwined. A prospective study of 233 men with Peyronie's disease found that 79% had co-existing ED by IIEF criteria 10. The fibrotic plaque impairs venous occlusion and may reduce arterial inflow to portions of the corpus cavernosum, contributing to vascular ED on top of any psychogenic component 11.

Four oral PDE5 inhibitors are approved by the FDA for ED: sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra, Staxyn), and avanafil (Stendra) 12. All four block phosphodiesterase type 5, the enzyme that degrades cyclic GMP in smooth muscle cells of the corpus cavernosum. Higher cGMP levels maintain smooth muscle relaxation and allow blood to fill the erectile tissue 13.

Beyond ED management, there is a biological rationale for PDE5 inhibitors having direct anti-fibrotic effects in Peyronie's plaques. Cyclic GMP signaling inhibits TGF-beta-1-driven fibroblast activation, the same pathway responsible for collagen overproduction in plaques 14. A 2010 prospective study (N=40) found that men taking daily tadalafil 5 mg for 6 months showed a statistically significant reduction in plaque size by ultrasound (P<0.05) compared with men who took tadalafil on-demand 15. The clinical magnitude was modest, and no head-to-head trial with CCH exists, but this finding informs the common clinical practice of prescribing daily low-dose tadalafil to men with Peyronie's disease who also have ED.

Sildenafil (Viagra) for Peyronie's-Associated ED

Sildenafil, sold as Viagra, was the first FDA-approved PDE5 inhibitor (1998) and remains the most widely studied 16. Standard doses are 25 mg, 50 mg, and 100 mg, taken 30 to 60 minutes before sexual activity. Onset typically occurs within 30 to 60 minutes; the therapeutic window extends roughly 4 to 6 hours 17.

A crossover trial (N=214) published in the New England Journal of Medicine found that sildenafil 50 to 100 mg produced successful intercourse in 69% of attempts versus 22% with placebo in men with broad ED etiology 18. Men with Peyronie's disease who have significant curvature may find positional adjustments necessary regardless of drug choice; sildenafil's shorter window can be an advantage when intercourse positions need to be adapted spontaneously.

High-fat meals delay sildenafil absorption by up to 60 minutes and reduce peak plasma concentration by approximately 29% 16. Common side effects include headache (16%), flushing (11%), and dyspepsia (7%) 17.

Tadalafil (Cialis) for Peyronie's-Associated ED

Tadalafil differs from other PDE5 inhibitors primarily in its half-life of approximately 17.5 hours, producing an effective window of up to 36 hours after a single dose 19. Available as 5 mg, 10 mg, and 20 mg on-demand doses, and as 2.5 mg or 5 mg for daily use 19.

The CIALIS RCT by Porst et al. (N=268) showed that tadalafil 20 mg achieved a mean IIEF-EF domain score improvement of 6.4 points versus 1.5 points with placebo (P<0.001) 20. For men with Peyronie's disease, the on-demand flexibility tadalafil provides is particularly practical: curvature can make intercourse timing unpredictable, and a drug that does not need to be taken to a tight clock reduces performance anxiety.

Daily tadalafil 5 mg is also FDA-approved for both ED and benign prostatic hyperplasia (BPH) 19. Many men with Peyronie's disease are over 50 and carry concurrent BPH; daily tadalafil addresses both. Tadalafil is less affected by food than sildenafil 19.

Vardenafil (Levitra, Staxyn) for Peyronie's-Associated ED

Vardenafil is the most selective PDE5 inhibitor among the original three agents, with approximately 10-fold greater selectivity for PDE5 over PDE6 compared with sildenafil 21. PDE6 inhibition in retinal photoreceptors is the mechanism behind sildenafil's transient visual disturbances; vardenafil's greater selectivity may translate to fewer visual side effects in some men 21.

A Phase III trial (N=601) found that vardenafil 10 mg and 20 mg improved the IIEF-EF domain score by 6.2 and 6.6 points respectively versus 1.9 points with placebo (P<0.001) 22. Onset is similar to sildenafil at approximately 30 to 60 minutes. Therapeutic duration is about 4 to 6 hours. Staxyn is an orally disintegrating tablet formulation of 10 mg vardenafil that dissolves on the tongue 23.

Men with Peyronie's disease who also carry a QTc prolongation risk should be cautioned: vardenafil produces a modest QTc prolongation of approximately 8 milliseconds at the 10 mg dose, a consideration absent from sildenafil and tadalafil labeling 23. Clinicians should review the patient's cardiac medication list before prescribing.

Avanafil (Stendra) for Peyronie's-Associated ED

Avanafil is the newest FDA-approved PDE5 inhibitor, approved in 2012, and it has the fastest onset of the four agents 24. Available in 50 mg, 100 mg, and 200 mg doses, avanafil can produce a response in as few as 15 minutes in some men, with a therapeutic window of approximately 6 hours 25.

The REVIVE trial (N=646) found that avanafil 100 mg and 200 mg produced successful intercourse rates of 57% and 59% respectively versus 33% with placebo (P<0.001) 25. Avanafil's high selectivity for PDE5 over PDE6 and PDE11 is associated with lower rates of back pain and muscle ache compared with tadalafil, and fewer visual disturbances compared with sildenafil 25. The 50 mg starting dose also gives a lower entry point for men who are sensitive to vasodilatory side effects.

For men with Peyronie's disease who require a spontaneous or rapidly initiated sexual encounter, avanafil's speed of onset makes it a reasonable first-choice PDE5 inhibitor pending individual tolerance 26.

Combining CCH with PDE5 Inhibitors: Clinical Approach

No randomized trial has specifically evaluated CCH plus a concurrent PDE5 inhibitor versus CCH alone. The clinical rationale is straightforward: CCH addresses curvature and plaque volume, while PDE5 inhibitors address the vascular and psychological components of ED that CCH does not reliably fix 27. Prescribing both in sequence, or concurrently after the immediate post-injection healing window, is standard practice in high-volume Peyronie's centers 28.

A practical sequencing approach used at many AUA-affiliated centers:

1. Complete the full CCH course (up to 4 cycles over approximately 24 weeks).
2. Reassess penile curvature by goniometry at 4 weeks after the final modeling session.
3. If residual curvature is below 30 degrees and the patient can have intercourse, add a PDE5 inhibitor for ED as needed or daily.
4. If curvature remains above 30 degrees after 4 CCH cycles, surgical correction (plication, grafting, or penile prosthesis) becomes the next conversation.

The AUA guideline recommends that clinicians offer a penile prosthesis to men with refractory Peyronie's disease and severe ED, noting that implant placement with intraoperative modeling can correct curvature simultaneously 2.

What CCH Cannot Do

CCH does not work on calcified plaques. Calcium deposits visible on ultrasound are resistant to enzymatic dissolution because the collagen structure has been replaced by hydroxyapatite 29. Ultrasound before injection is not required by the FDA label but is recommended by most urologists to exclude calcification at the injection target site 2.

CCH also does not correct penile shortening caused by dense scarring. Some men experience additional shortening during the acute post-injection phase. The penile stretching protocol provided after each cycle is partly intended to minimize length loss over the course of treatment 30.

Men whose primary complaint is length loss rather than curvature may not see meaningful benefit from CCH and should discuss traction therapy devices (Class II medical devices for Peyronie's) or surgical options with their urologist 31.

Insurance Coverage and Cost Considerations

Xiaflex costs approximately $3,700 to $4,200 per injection vial before insurance discounts, and each treatment cycle requires two vials 32. A full 4-cycle course can exceed $30 to 000 in drug costs alone, excluding physician fees and facility charges. Most major commercial insurers and Medicare cover Xiaflex for Peyronie's when the patient meets label criteria, but prior authorization is almost always required 33.

Endo Pharmaceuticals offers a patient assistance program (Xiaflex Patient Support Solutions) for uninsured or underinsured patients. Generic CCH is not available. The manufacturer's savings card may reduce out-of-pocket costs for commercially insured patients to a stated maximum of $0 per injection for eligible patients, subject to program terms.

PDE5 inhibitors, by contrast, are substantially cheaper as generics. Generic sildenafil costs as low as $0.50 to $2.00 per tablet at most pharmacies. Generic tadalafil is similarly priced 34. Avanafil and brand-name vardenafil (Levitra) remain branded only at the time of writing and carry higher costs.

Monitoring After Treatment

After completing CCH cycles, the treating urologist should document final curvature by standardized goniometry (stretched or erect penile photography) and reassess IIEF scores. A 2016 follow-up analysis of IMPRESS participants found that curvature improvements were maintained at 52 weeks, with no significant loss of the initial response over the study follow-up period 35.

Men who achieve satisfactory curvature reduction but have persistent ED should be offered a PDE5 inhibitor with a clear explanation of expected response rates. Sildenafil 50 mg on-demand achieves a satisfactory erection in approximately 65 to 70% of unselected ED patients in meta-analyses 36. Response rates are lower in men with severe vascular ED or after radical prostatectomy, where higher doses or daily tadalafil are typically preferred 37.

Men whose Peyronie's disease is not adequately controlled after 4 CCH cycles should be referred for surgical consultation. Surgical options include penile plication (Nesbit or modified procedures), plaque incision and grafting, or placement of an inflatable penile prosthesis, each with distinct trade-offs in penile length, rigidity, and durability 38.