Clinical Studies
We have initiated Phase IIb clinical trials for STP705 for isSCC in the U.S. in May 2021. We filed our IND in China for a Phase IIb clinical trial for isSCC that would be part of a global multicenter clinical trials. We have initiated Phase II clinical trials for BCC in December 2020 and Phase I/II clinical trials for keloid scar recurrence post-keloidectomy in April 2021 in the U.S. We initiated Phase I/II clinical trials for HTS in the U.S. and expect to file an IND for a Phase II clinical trial in China in the second half of 2022. We intend to initiate the clinical trials in China led by a Chinese principal investigator because the demand for treatment of HTS is stronger in China than the U.S. We have also initiated Phase I clinical trials for STP705 in the U.S. in March 2021 for CCA, HCC or liver metastases in patients with advanced/ metastatic or surgically unresectable solid tumors who are refractory to standard therapy and expect to file an IND in China as part of global multicenter clinical trials.

Our Phase IIb clinical trials for STP705 for isSCC will further evaluate the two most efficacious dosing regimens identified in our Phase IIa clinical trial in a randomized, doubleblind, placebo-controlled study in up to 100 adult patients with isSCC. The primary endpoint for the trial is proportion of participants with histological clearance of treated isSCC lesion at the end of treatment. Histological clearance will be defined as the absence of detectable evidence of isSCC tumor cell nests as determined by central pathology review. We performed dose administration for our first patient in the U.S. in June 2021. We anticipate an interim data readout in the first half of 2022.

After completion of the Phase IIb trial for STP705 for isSCC, subject to continued efficacy and safety results as seen in our previous isSCC study, we anticipate participating in a meeting with FDA where we will receive FDA guidance for our further clinical development plan, including but not limited to such things as FDA’s expectations for efficacy endpoints required for an NDA application and subsequent approval, as well as the number and size of Phase III trials required for NDA registration for the use of STP705 for the treatment of isSCC.

Our Phase I/II clinical trial for STP705 for keloid scar prevention will evaluate the safety and efficacy of various doses of STP705 when injected intradermally into a keloid excision site to prevent the recurrence of keloids in adult patients in a randomized, double-blind, multiple-arm, controlled study in 50 patients. The primary endpoint of this trial is to measure the rate of recurrence in patients who have undergone keloidectomy surgery alone (receiving placebo) versus surgery and administration of STP705 at three months, six months, and 12 months post-surgical excision. We performed dose administration for our first patient in the U.S. in May 2021. We expect to report initial clinical data in the first half of 2022.

Our Phase II clinical trial for STP705 for BCC will evaluate the safety and efficacy of intralesional injection in adult patients with cutaneous BCC confirmed with biopsy samples in an open-label, dose escalation study of at least 15 patients. Participants will receive injections of STP705 once a week for up to six weeks. The primary endpoint for the study is to evaluate patients for complete histological clearance of the tumor cells within the treated BCC lesion with secondary endpoints, evaluating subjects for investigational product treatment related adverse events, as well as serious adverse events, and cutaneous skin reactions. We performed dose administration for our first patient in the U.S. in January 2021.

Our Phase I clinical trial for STP705 in liver cancer will evaluate the safety, tolerability, pharmacokinetics, and anti-tumor activity of intratumoral administration of STP705 in a “basket study” of patients suffering from CCA, HCC or liver metastases from other cancers for patients with advanced/metastatic or surgically unresectable solid tumors who are refractory to standard therapy. The subjects in this study have previously failed multiple rounds of standard of care therapy including novel oncology drugs and traditional chemotherapies and thus represent a very resistant class of tumor. The study is an open-label, dose escalation study of up to 50 patients. In order to determine the maximum tolerated dose (MTD), up to 30 patients (6 per cohort) will be enrolled in the dose escalation phase of the trial, during which cohorts will be assigned to receive doses of 20 μg, 40 μg, 80 μg, 160 μg, and 320 μg doses of STP705 administered via intra-tumoral injection on days 1, 8 and 15 of a 28 day cycle. Once the MTD is achieved, up to 20 more subjects will be enrolled to confirm safety and explore anti-tumor activities.

The primary endpoints are (i) to determine the MTD of STP705 when administered via intra-tumor injection and (ii) to establish the dose of STP705 recommended for future Phase II clinical trials when administered via intra-tumor injection. The secondary endpoints include determination of the pharmacokinetics (PK) of STP705, evaluation of tumor infiltrating lymphocytes at the site of STP705 administration, and observation of preliminary antitumor activity of STP705 at the site of administration and at other sites of disease.

We performed dose administration for our first patient in our liver cancer trial in June 2021. If subjects exhibit stable or improvement in tumor they will be treated with subsequent treatment cycles. If subjects exhibit advancing disease, they will be discontinued from study. We have completed cycle 4 for the first subject in our 20 μg cohort, and this subject exhibits stable disease in the treated tumor and will continue to cycle 5. We have completed cycle 3 for the first subject in our 40 μg cohort; this subject has exhibited stable disease in the treated tumor, but has developed a new lesion outside the liver and thus will be discontinued from the study. These subjects suffer from HCC and metastatic colon cancer, respectively. There have been no treatment related AEs or SAEs. We expect to complete the dose escalation phase in the first half of 2022.

We are developing combination therapies with STP705 and immune checkpoint therapeutics for liver cancer. We are currently exploring the efficacy of combination therapy with STP705 and anti-PD-L1 targeted therapies in preclinical studies. We are collaborating with Innovent to conduct preclinical studies in the U.S. directed to combination therapy using STP705 and sintilimab, a novel anti-PD-1 monoclonal antibody approved by the NMPA for use in treatment of advanced cancers, such as NSCLC. We are also collaborating with Shanghai Junshi to conduct preclinical studies in the U.S. directed to combination therapy using STP705 and Shanghai Junshi’s novel anti-PD-1 monoclonal antibody approved by the NMPA for use in treatment in advanced melanoma, squamous cell carcinoma and other indications.