Tuesday, 19 February 2013

Xiaflex Phase III Study



The Investigation for Maximal Peyronie’s Reduction Efficacy and Safety Studies (IMPRESS) I and II examined the clinical efficacy and safety of collagenase clostridium histolyticum (CCH) intralesional injections in subjects with Peyronie’s disease (PD). Co-primary outcomes in these identical phase 3 randomized, double-blind, placebo-controlled studies included percent change in penile curvature deformity and change in Peyronie’s Disease Questionnaire PD symptom bother score from baseline to 52 weeks.

Materials and Methods

The IMPRESS I (N=417) and II (N=415) studies examined CCH intralesional injections through a maximum of 4 treatment cycles, each separated by 6 weeks. Subjects received up to 8 injections of 0.58 mg CCH, 2 injections per cycle separated by approximately 24-72 hours, with the second injection in each followed 24-72 hours later by penile plaque modeling. Subjects were stratified by degree of penile curvature at baseline (30-60° versus 61-90°) and randomized to CCH or placebo (2:1 in favor of CCH).


From a post-hoc meta-analysis of IMPRESS I and II data, CCH-treated subjects showed a mean 34% improvement in penile curvature deformity, a mean -17.0±14.8° change per subject, compared with a mean 18.2% improvement in placebo-treated subjects, a mean -9.3±13.6° change per subject. Mean change in PD symptom bother score was significantly improved in CCH-treated (-2.8±3.8) versus placebo (-1.8±3.5, p=0.0037) subjects. Three corporal rupture serious adverse events occurred and were all surgically repaired.


The IMPRESS I and II studies support the clinical efficacy and safety of CCH treatment for both the physical and psychological aspects of PD.



These results, while not astonishing are worth taking note of. Men who received Xiaflex injections as part of the Phase III study had a mean improvement of  34% vs 18% for those in the placebo group. This compares to a mean improvement of 29.7% in penile curvature and 11% for placebo in the Phase IIB study. This suggests to me that both the structure of the program and skill of the doctor injecting are meaningful factors when we're talking about outcomes.

The positive results for the placebo treated patients is, as it has been in previous Xiaflex studies, somewhat perplexing. It may be that the tendency to experience spontaneous improvement is greater than thought, though more likely is that the penile 'modelling procedure' (traction therapy) which forms part of the regimen, is responsible for the improvement . I'll keep an open mind about it. In either case, the take home from this is that Xiaflex isn't a miracle drug but certainly can help to reduce curvature of the penis. Side effects can be an issue with some men though, so it's all about what's right for the individual. These results are set to be published in the Journal or Urology mid way through the year.

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