Abstract: Rose Bengal is a novel injectable agent that has been evaluated as a rational treatment strategy for melanoma patients with recurrent unresectable local/regional metastases accessible for intralesional injection. PV-10 (10% Rose Bengal) has completed phase 1 and phase 2 multi-center clinical trials demonstrating significant local/regional disease control and also responses in non-injected regional bystander lesions and distant metastases. The published results of studies that have assessed PV-10 are presented, and the rationale for combining its use with recently approved immunotherapeutic agents is discussed.See the link to the paper here. The digital version provided by Provectus on its website reached the maximum number of users/views allowed (i.e., too many views), however. The company will have to up this number for more folks to read it. I discussed the paper when it was first published online; see blog news item Journal Publication (February 11, 2014) under the Archived News tab.
A blog reader further highlighted his takeaways from Ross' paper:
- "In addition to an excellent safety profile, encouraging results were observed, including effective local tumor ablation, bystander responses in un‐injected lesions, and unexpectedly prolonged delays in disease progression, particularly in patients who were observed to have local tumor destruction. These latter observations suggested an induced systemic immune response elicited by the tumor ablation."
- "These observations suggest that tumor necrosis may lead to a robust specific anti‐tumor host immune response. The effects of released tumor antigens on nearby antigen presenting cells may facilitate the presentation of specific antigenic targets to circulating T and B cells. The potential for chemokine release and local inflammation in response to granulocyte destruction may enhance the host response. Interestingly, spontaneous involution of untreated tumors was observed in a mouse hepatocellular homograft model and closely correlated with effective ablation of injected target tumors. These observations support the induction of a tumor‐specific host immune response."
- "Furthermore, unexpected long‐term survival was observed in the patients achieving a response compared to similarly staged patients receiving other therapeutic modalities. These observations strongly support the concept that effective tumor ablation can elicit an effective anti‐tumor systemic response."
- "Because of easy access to the local/regional disease, intralesional agents have been studied, but only recently with the rigor of formal prospective trials. IL PV‐10, is well tolerated, easy to administer, and based on Phase 1 and 2 data has an established and excellent safety profile, and results in meaningful responses in injected lesions and untreated bystander lesions. IL PV‐10 compares favorably with the published experience with the vast majority of other injectable agents in terms of side effects and local disease control."
Further study of PV‐10 is certainly warranted either in the context of a phase 3 trial, or as a phase 1/2 study in combination with the checkpoint blocking agents or vaccines. The goal of these phase1/2 trials would be to document the safety of these novel combinations and demonstrate enhanced local/regional response and disease control as well as an augmentation of the systemic anti‐tumor responses. The success of such trials would further advance the melanoma treatment landscape.Dr. Ross has been involved with the company for several years, and MD Anderson has been a compassionate use program ("CUP") site on and off since about 2009. Interestingly, it only was since March 2014 (around the time Provectus announced it had submitted its breakthrough therapy designation application ["BTD"]) that the cancer center was named a CUP site on clinicaltrials.gov. See my blog post Provectus Submits Application to FDA for Breakthrough Therapy Designation. As I noted in blog news item Various (July 30, 2014), MD Anderson noted Provectus' CUP in its August 2014 Melanoma Horizons newsletter, following ASCO 2014 and BTD denial.
Per my blog news item Provectus increases cash balance (July 31, 2014) it would appear the company has increased the amount of cash on its balance sheet, by virtue [I believe] of management writing "Cash on hand supports planned operations until 2016" (rather than its previous comment as late as July 28th of "Cash on hand supports planned operations until 2015"). In my blog post 2014 Annual CEO Letter (pt. 1) I wrote:
Without consideration of the melanoma Phase 3 trial, the projected cash balance should look something like the below. At a projected $2.5 million average quarterly burn, Provectus would approach its accounting firm BDO LLC's minimum cash threshold figure of about $4 million in the 4Q15 timeframe (potential fund raising would occur before that so the threshold is not met of course).
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Provectus' June 12th 8-K detailing the settlement of the shareholder derivative lawsuit noted a date of July 24th for a hearing on the terms of the proposed settlement. Depending on how much is paid back by management (i.e., ~$4.5 million or ~$9 million), the additional cash should provide further runway for the company to reach the trial's interim readout and make its case to the Agency for filing the NDA. Below, for example, I assume these monies are paid back in 3Q14. Without consideration of the melanoma Phase 3 trial, the projected cash balance would look something like the below. At a projected $2.5 million average quarterly burn, Provectus would approach its accounting firm BDO LLC's minimum cash threshold figure of about $4 million in the 1Q16 timeframe, assuming repayment of the lower amount (the higher payment obviously provides at least an additional quarter of runway).
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"AstraZeneca has managed to be included in the pioneering group of players working on immune checkpoint inhibitors, which prominently features competing teams from Bristol-Myers Squibb ($BMS) (nivolumab), Merck ($MRK) (pembrolizumab) and Roche ($RHHBY) (the rival PD-L1 drug MPDL3280A.) Merck has been the leader in the partnering arena, executing a long lineup of collaborations. But all the players see combo treatments as the big second wave in R&D, with immuno-oncology treatments dismantling the protective screen cancer cells use to hide from the immune system and other drugs spurring an attack."
The plan B path to approval, albeit a very reticent one in the past, was to allow PV-10 to be combined with checkpoint inhibitors, initially anti-CTLA-4 agents (early on tremelimumab before it was out-licensed by Pfizer to AstraZeneca/MedImmune in 2011, later following approval ipilimumab) but now anti-PD-1 agents (at the moment both Bristol-Myers' nivolumab and Merck's pembrolizumab). Moffitt Cancer Center as recently as ASCO 2014 said/wrote in/on their PV-10-related abstract/poster: "IL PV-10 may be rationally combined with systemic immunotherapy for the treatment of metastatic melanoma." Moffitt later repeated the statement at a presentation during the 4th European Post-Chicago Melanoma Meeting: Interdisciplinary Global Conference on News in Melanoma. One of management's reservations has been paying for or materially contributing to the expense of such a combination study. The checkpoint inhibitors range in cost from $100,000 to over $200,000; see my blog news item % CR per thousand dollars of treatment cost (February 6, 2014) under the blog's Archived News tab. The total cost of treatment for several treatment courses over whatever prescribed time period for a combination study would be much more (the above costs are for a single course). There also are investigator, site and other customary costs of running a trial. If management were to agree to combine PV-10 with, say, nivolumab or pembrolizumab, they presumably would require (unless their current stance is materially different from their historical one) the partner to pay for most if not all of the study's cost save for Provectus' contribution of PV-10 drug product.
Moffitt's Dr. Jeffrey Weber, M.D., Ph.D. is a notable proponent of combination therapy (quotes below are from a December 2013 interview/article):
- "If you use [BRAF drugs] sequentially, it isn’t as good as using them in combination. The way to deal with metastatic melanoma is to hit it hard upfront rather than treat them, wait for resistance, then try to overcome resistance. So the best way to approach treatment is to hit them hard, hit them quick, and hit them often. Melanoma is a difficult disease, and backing off is a sure-fire way to not benefit the patient."
- "I think community oncologists should also consider patients for combination BRAF inhibitor trials—not just treat them on vemurafenib, but consider them for a trial of combination therapy. The combination therapies are all investigational, of course. You can always treat someone with vemurafenib, but they are almost always going to progress. So why not try to do something where they may not progress? And I would send patients for combination ipilimumab/PD-1 trials, because it turns out that the combination, despite a fair amount of toxicity, has a very impressive response rate. Many patients become complete responders, which is very encouraging. I think there are many good combination therapy trials under way, as well as trials with adoptive cell therapy, that look very promising to me."
- "If you combine blocking of CTLA-4 in the mouse with some sort of vaccine strategy, tumors could be cured. In fact this was seen in some tumors that otherwise were very difficult to treat in the mouse model. This was studied around 2001, and initial studies were at the National Institutes of Health and in Los Angeles, where I was at the time."
I think the "tough" part of any combination study is to finalize the sequencing of PV-10 and the partnered checkpoint inhibitor. I wrote about likely combinations in my blog post Combinations & Permutations, Sequencing. Weber's important Big Pharma relationships include Bristol Myers and Merck. For combination study relationships to be struck with Provectus for PV-10, I would presume Moffitt's pre-clinical work on combining the drug with checkpoint protein inhibitors will have to be front and center, Dr. Weber and Moffitt will have to play a key (primary) role in carrying the work out, there would have to be strong interest on the part of prospective partners, and small or little expense would have to be incurred by Provectus.