Therapeutic cancer vaccines
Regeneus has developed autologous cancer vaccines from technology licensed from the Kolling Institute of Medical Research. The technology involves the removal of a tumour or biopsy from the ‘patient’ (dog/human) as source material to produce a personalised vaccine, which stimulates the immune system to see cancer cells as foreign, prompting T-cells to attack the tumour cells. The vaccine is potentially applicable to a wide range of solid tumour types.
RGSH4K human cancer vaccine
Regeneus initiated the ACTIVATE Phase I trial of its RGSH4K human therapeutic cancer vaccine in mid-2015. ACTIVATE is a single-centre, open-label, dose-escalating study of the safety and preliminary efficacy of the vaccine. The trial will recruit 21 patients with a range of advanced cancers. Recruitment had been anticipated to be completed in Q4 CY16, but the 2016 AGM presentation indicated that recruitment was expected to be completed in H1 CY17.
Recruitment of patients to bank tumour samples for preparation of the vaccine has gone well, but patients only receive RGSH4K injections when they reach end-stage disease after having exhausted all standard treatments, so the timing of subject dosing is difficult to predict.
Assuming that the Phase I trial reports results in 2018, an accelerated approval in the US under the 21st Century Cures Act could potentially be achieved in 2022 following completion of a Phase II trial. On the other hand, if a Phase III efficacy trial is required, then approval could be achieved in 2026. In our indicative valuation of RGSH4K we currently assume approval in 2024, the midpoint between these two scenarios.
Regeneus intends to explore the opportunity to combine RGSH4K with the immune checkpoint inhibitor (ICI) class of drugs. RGSH4K is designed to initiate an immune response, while the ICI drugs effectively “take the handbrake off” immune responses making them more potent, so the combination of the two approaches could potentially stimulate highly effective immune responses against cancer cells.
Regeneus has indicated that it is exploring partnering opportunities for RGSH4K in combination with ICIs. In our view, it is likely that efficacy trials would combine RGSH4K with an ICI such as Keytruda (pembrolizumab, Merck), Opdivo (BMS) or Tecentriq (Roche), or one of the ICI drugs that is currently in development.
RGSH4K uses a chemical modification of the patient’s own tumour proteins to couple them to a bacterial adjuvant to make them more immunogenic. This relatively simple manufacturing process would be expected to translate to a low cost of manufacture for a personalised cancer vaccine.
A number of companies are already studying cancer vaccines in combination with ICI therapy. For example, Merck and Agenus are collaborating in a Phase II trial of Keytruda in combination with Agenus’s Prophage autologous cancer vaccine in glioblastoma. Merck has also combined Keytruda with Genexine’s cancer vaccine GX-188E in clinical trials in HPV-induced cancer. BMS is testing Opdivo with Bavarian Nordic’s CV301 and Prostvac in non-small cell lung cancer and prostate cancer respectively, while Roche is investigating Tecentriq in combination with BioNTech’s personalised cancer vaccine.
ICIs that are still in development are also being combined with cancer vaccines. For example, Merck and Pfizer are testing their PD-L1 drug avelumab alongside Transgene’s TG4001 cancer vaccine, while AstraZeneca is combining the PD-L1 inhibitor durvalumab with a cancer vaccine from TapImmune in ovarian cancer.
Osteosarcoma trial suggests Kvax canine cancer vaccine improves survival
In addition to the RGSH4K human product, Regeneus is also developing a therapeutic cancer vaccine for use in dogs, known as Kvax. The company conducted a marketing study of Kvax in conjunction with Dr Phil Bergman of VCA, the largest veterinary services group in the US, to generate real-world clinical study results in osteosarcoma. Thirteen dogs with osteosarcoma were treated with multiple doses of Kvax following amputation of the affected limb. The median progression-free interval (PFI) was 125 days and median overall survival (OS) was 182 days. The investigator concluded that Kvax was well tolerated and appears to confer improved PFI and OS compared to a historical control group.
Regeneus is currently recruiting subjects in a separate trial of Kvax in 45 dogs with lymphoma, which began in November 2015. The double-blind, placebo-controlled trial, being conducted by veterinary oncologists at the Small Animal Specialist Hospital in Sydney, Australia, will use Kvax together with chemotherapy to seek to extend remission times in dogs that initially respond to chemotherapy. Lymphoma is the most commonly treated cancer in dogs; remission typically lasts eight to 10 months with chemotherapy, with a median survival of about one year.
Regeneus has been advised by the Center for Veterinary Biologics at the US Department of Agriculture that it can commercialise Kvax in the US without obtaining specific regulatory approval. We do not expect the product to be launched commercially until further efficacy data are available to support marketing efforts.