MP37-14: A Dose-Escalating Phase I Study of an Injection of Lidocaine Paste for Prolonged Spermatic Cord Block in Men with Chronic Scrotal Content Pain

Luke Witherspoon*, Claudia Kesch, Veronika Schmitt, Graeme Boniface, Colin Lundeen, Vancouver, Canada, J. Curtis Nickel, Kingston, Canada, Ryan Paterson, Martin Gleave, Ryan Flannigan, Vancouver, Canada

Introduction: Spermatic cord block with local anesthetics provides pain relief in a subset of subjects with chronic scrotal content pain (CSCP), but relief is short-lived due to the rapid elimination of local anesthetics. This Phase I trial assessed the safety, tolerability, pharmacokinetics and efficacy of a long-acting formulation of lidocaine in patients with CSCP.

Methods: This was a prospective, single center, open label, single arm, Phase I dose-escalating trial. Male patients = 19 years with unilateral scrotal pain lasting = 3 months who reported an average daily maximum pain score over 7 days of = 4 on a 0-10 numerical rating scale (NRS) were recruited. 

The investigational drug ST-01 (sustained-release lidocaine polymer solution for injection) is a long-acting lidocaine injected into the spermatic cord. ST-01 has two inactive ingredients, polyethylene glycol (PEG) and poly(lactic-co-glycolic acid) (PLGA) which  slow the release of lidocaine. The study had 3 planned dose-escalating cohorts: cohort I: 2 mL of 140 mg/mL ST-01 (280 mg lidocaine); cohort II: 3 mL of 140 mg/mL ST-01 (420 mg lidocaine); cohort III: 4 mL of 140 mg/mL ST-01 (560 mg lidocaine). Subjects recorded their pain (NRS) three times a day on days 0 – 14, and once on days 15-27 of the study. The Chronic Epididymitis Symptom Index (CESI) was completed by patients on days 0, 7, 14, and 28 (end of study).

Results: Twenty subjects were screened, with 12 subjects being enrolled. NRS (mean, median) was reduced across all cohorts studied. Patients in cohort II (420 mg lidocaine) were identified via the dose escalation protocol. This group reported a baseline mean (median) NRS score of 5.3 (5), compared to an end of study score of 3.3 (3.5). Assessment of CESI score showed reduced scores over the study period with cohort II reporting a baseline mean (median) score of 19.8 (19) and an end of study value of 16.8 (17.5). Serum lidocaine concentrations were measured at 1 hour, 1 day and 7 days. Serum concentrations were similar across all cohorts at day 1 indicating only local release of the medication. There were no serious adverse events (SAE’s) reported in the study. All subjects reported at least one treatment-emergent adverse event (TEAE). Most TEAE’s were mild or moderate and related to bruising or swelling at the injection site.

Conclusions: ST-01 was safely injected in 12 subjects suffering from CSCP with a promising efficacy signal.

Source of Funding: This study was conducted with aid from the Vancouver Coastal Health Research Institute Translation and Innovation Award.