Sorrento Therapeutics, Inc. announced positive Phase 2a top-line clinical trial results for the RTX program. The Phase 2a study follows the positive observations from the Phase 1b/2 trial results (NCT03542838) of RTX Day 84 patient data, for which Sorrento has completed the one-year follow up for the last patient dosed in February 2021. The phase 2 trial, a multi-center, double blind, placebo- and active-controlled study, assessed the efficacy and safety of several dose groups of RTX to manage pain in patients with moderate-to-severe OAK.

Given the durability of OAK pain relief response to RTX demonstrated in earlier phase 1b/2 trials, Sorrento decided to include an active approved comparator (Zilretta® intra-articular corticosteroids) in the current trial protocol. Generally, treatment was well-tolerated, with the most common noted AE being pain following topical capsaicin 0.1% given to all patients for blinding purposes and study drug administration in the knee (across all dose groups). Very few serious AEs were noted across all dose groups, with one in particular in the 15mcg RTX group being severe/life threatening (hypertension following drug administration), which resolved within hours with treatment of pain and no additional intervention.

In the cases requiring pain control (any group) the dose of opioid was comparable. A few subjects in RTX groups required use of low dose oral opioids for up to 6 hours in some cases of prolonged moderate discomfort/pain. No patient required additional pain control or intervention after 6 hours or in the days following the day of administration and no patient left the clinic with opioids or an opioid prescription.

The RTX 20mcg dose group performed best among all dose groups, including placebo (lidocaine only) and approved intra-articular corticosteroid (Zilretta) on short-term and prolonged pain relief measures (SPID, KOOS, WOMAC). Although at many time points, RTX 20mcg was statistically significant as compared to the approved drug (Zilretta®) in this indication active control, we note that the study was not powered to demonstrate statistical significance for all end points listed (primary, secondary), with only 120 patients enrolled across 5 RTX dose groups and early terminations due to the Company?s previously announced bankruptcy proceedings. Despite the limitations of the study (small number of patients per group, high variability of placebo responders due to intra-articular use of 10ml lidocaine and capsaicin cream for blinding per FDA request), the results = demonstrate that RTX 20mcg is an effective pain treatment for longer durations (up to one year), with better score improvements at week 26 and 52 than the current standard of care (active steroid injection.

Zilretta) up to and past week 26. A higher proportion of patients responded to treatment with RTX 20mcg than any other treatment group, including Zilretta. Reduction in pain was also more pronounced with RTX 20mcg than with any other treatment group, including placebo and active control.

Durability of treatment was nearly twice as long for RTX 20mcg than active steroid control (mean time to return to 10% of baseline of 19 weeks for RTX versus 10 weeks for Zilretta). In conclusion, we report that the phase 2a OAK study for RTX has met all the primary and secondary objectives for the study. The Phase 2a results were consistent with the prior safety profile of the drug from the previously completed Phase 1 study and has allowed for the potential determination of a therapeutically effective dose for further phase 2 pivotal or phase 3 studies, which is expected to be powered with a sufficient number of patients to provide significantly different results from the controls.