The Early Obsolescence of Checkpoint Inhibitors

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Take as a starting point Inman et al.’s 2007 article entitled Costimulation, coinhibition and cancer, and their statement therein: (underlined emphasis is mine):

“If sufficient co-stimulation is provided in the presence of adequate tumor-associated antigenic stimulation, the immune system will act against tumor antigen and, thus, destroy early tumors before they become fully established. Contrarily, if co-inhibitory signaling dominates, the immune system will be tolerized to tumor antigens, and the tumor will be permitted to grow unfettered and unmolested by the immune system. If neither co-stimulatory nor co-inhibitory signals dominate, the adaptive immune system may remain in a tenuous state of equilibrium, militating against tumor outgrowth with varying degrees of success.”

The essence of the authors’ view might be that the immune system is capable of decisively acting against cancer only in the situation where or circumstance that co-stimulation dominates co-inhibition. Take also as context to this starting point, however, that what we don’t know about the immune system probably dwarfs what we know about it.

The notion of “releasing the brakes” in the medical literature and mainstream press describes the approach of inhibiting cancer’s ability to suppress or block the body’s immune system from acting, and thus to evade attack. Although possibly coined in the early-2000s (see, for example, Tirapu et al.’s 2002 article entitled Effective tumor immunotherapy: start the engine, release the brakes, step on the gas pedal,...and get ready to face autoimmunity), use of the releasing-the-brakes phrase may have grown more widespread starting in the late-2000s and around the time of Dr. James Allison, Ph.D’s seminal work of blocking (inhibiting) the CTLA-4 protein receptor (using Bristol-Myers’ ipilimumab) and, later, the follow-up scientific exploration of blocking (inhibiting) PD-1 and PD-L1 ligands too (and associated PD-1 therapeutics pembrolizumab and nivolumab, for example, from Merck and Bristol-Myers, respectively).

Medical literature has more sparsely touched on, and mainstream press much less so, the other two components of the get-the-car-moving analogy (where the car is the immune system), “starting the engine” and “stepping on the gas pedal,” where these phrases relate to different aspects of stimulating the body’s immune system.

Possibly over-using the car analogy further, with the potential risk of over-simplifying it inappropriately, consider T cell immunity as a car at rest. More immunogenic tumors and their associated cancers like melanoma are like a car sitting on a slight incline. Release its brakes by treating the tumors (and thus the cancer) with checkpoint inhibitors, and the car may roll forward move some distance, notable or otherwise. With other less or non-immunogenic cancers, think of the car as sitting on a flat surface. Releasing the brakes does not enable the car to move any meaningful distance, if at all.

If you want to get the car to really move, you have to start its engine, and then step on its gas pedal. Releasing the brakes might help the car move farther and faster, but it also is quite possible the car may be able to move sufficiently without the need for further action other than to start its engine and/or stepping on its gas pedal.

The continued use of get-the-car-moving analogy of course requires the assumption the car can drive by itself; that is, the immune system can handle its own business once it has been started, and is appropriately up and running from stepping on the gas pedal.

Now consider Winograd et al.’s 2015 article entitled Induction of T cell immunity overcomes complete resistance to PD-1 and CTLA-4 blockade and improves survival in pancreatic carcinoma. In particular, note the underlined sentences (my emphasis) from the article’s abstract:

“Disabling the function of immune checkpoint molecules can unlock T cell immunity against cancer, yet despite remarkable clinical success with monoclonal antibodies (mAb) that block PD-1 or CTLA-4 resistance remains common and essentially unexplained. To date, pancreatic carcinoma is fully refractory to these antibodies. Here, using a genetically engineered mouse model of pancreatic ductal adenocarcinoma in which spontaneous immunity is minimal, we found that PD-L1 is prominent in the tumor microenvironment, a phenotype confirmed in patients; however, tumor PD-L1 was found to be independent of IFN-γin this model. Tumor T cells expressed PD-1 as prominently as T cells from chronically infected mice, but treatment with PD-1 mAb, with or without CTLA-4 mAb, failed in well-established tumors, recapitulating clinical results. Agonist CD40 mAb with chemotherapy induced T cell immunity and reversed the complete resistance of pancreatic tumors to PD-1 and CTLA-4. The combination of αCD40/chemotherapy plus PD-1 and/or CTLA-4 induced regression of subcutaneous tumors, improved overall survival, and confered curative protection from multiple rechallenges, consistent with immune memory not otherwise achievable. Combinatorial treatment nearly doubled survival of mice with spontaneous pancreatic cancers although no cures were observed. Our findings suggest that in pancreatic carcinoma, a non-immunogenic tumor, baseline refractoriness to checkpoint inhibitors can be rescued by the priming of a T cell response with αCD40/chemotherapy.”

CD40 is a co-stimulatory protein, while chemotherapy has been understood to act in a stimulatory fashion through the subsequent release of cancer antigens.

Achieving T cell immunity almost if not actually by definition should mean overcoming resistance to cancer, thus overcoming checkpoint blockade and mitigating the need to artificially release the brakes.

Should stimulation via stimulatory therapeutics and therapies start the engine and enables the gas pedal to be stepped on sufficiently and appropriately (i.e., with minimal or manageable side effects or adverse events) so as to achieve T cell immunity, brakes may not be necessary once the car is moving (in context, and given the car [the immune system] can drive itself and not careen off the road because it then should know what it is doing).

Over time, however, road friction may start slowing the car down to the point where waning immunosurveillance (the immune system recognizing and eliminating continuously arising cancerous cells) no longer can protect the patient from relapse (analogous to how waning varicella zoster antibody titers may result in a bout of shingles). Keeping the brakes disengaged, especially with non-immunogenic tumors, should have some role going forward, making Merck, Bristol-Myers, Roche, AstraZeneca, Pfizer and other companies’ checkpoint inhibitors not necessarily obsolete as much as persnickety.

Bristol-Myers vs. The Field (ex-Provectus)

Last week Bristol-Myers filed a lawsuit against Merck over [anti-]PD-1 agent pembrolizumab (trade name Keytruda), which was approved last week by the FDA for late-stage or metastatic melanoma.

Specifically, Bristol-Myers claims that Merck is violating the patent on its Opdivo mediation for tackling melanoma, which was recently approved in Japan and became the first so-called PD-1 inhibitor to win regulatory backing anywhere. A PD-1 inhibitor blocks a protein that acts as a brake on certain immune system cells and prevents them from attacking healthy tissue. (Bristol-Myers Sues Merck Over a Patent on its new Cancer Drug, The Wall Street Journal, September 8, 2014)

Merck disclosed PD-1 antibody patent oppositions and litigation, at the time in Europe, in its 10-Q filing for the period ending June 30, 2014 (see page 22):

As previously disclosed, Ono Pharmaceutical Co. (“Ono”) has a European patent (EP 1 537 878) (“’878”) that broadly claims the use of an anti-PD-1 antibody, such as the Company’s immunotherapy, pembrolizumab (MK-3475), for the treatment of cancer. Ono has previously licensed its commercial rights to an anti-PD-1 antibody to Bristol-Myers Squibb (“BMS”) in certain markets. The Company believes that the ‘878 patent is invalid and filed an opposition in the European Patent Office (the “EPO”) seeking its revocation. In June 2014, the Opposition Division of the EPO found the claims in the ‘878 patent are valid. The Company expects to receive the Opposition Division’s written opinion in the third quarter of 2014, after which it will begin the appeal process. {Underlined emphasis is mine}

As FiercePharma's Tracy Staton writes: "The lawsuit asks for damages, but more importantly, asks the court to declare that Merck infringes that PD-1 patent. Such a decision would bolster Bristol-Myers and Ono's argument that they are owed royalties on sales of rival PD-1 drugs."

As I wrote in my Why Keytruda's approval is a good thing for PV-10 (September 8, 2014) news item under the blog's News tab:

KOLs see PD-1s as treating the bulk of late stage cancer. Key opinion leaders ("KOLs") see PD-1s, which fall under the category of checkpoint protein inhibitors that also include CTLA-4 and PD-L-1 agents, as an improvement over CTLA-4 agents like approved ipilimumab (trade name Yervoy) and tremelimumab. KOLs will use PD-1s to treat as many indications as they can scientifically support. Abstracts of Merck oncology-sponsored pembrolizumab studies being presented at ESMO 2014 in late-September, for example, include bladder and gastric cancer, advanced melanoma, non-small cell lung cancer ("NSCLC"), and head and neck cancer.

Bristol-Myers and Merck's PD-1s are projected to play key roles in the supposed several tens of billions of dollars equity research analysts estimate will be derived from the immuno-oncology addressable market.

But KOLs believe the more dominant use of PD-1s will come from combining them with other drugs to treat late-stage cancer, rather than strictly using them as monotherapies. I summarized 14 previously announced and/or conducted combination studies below, and first in my Combinations (July 24, 2014) news items under the blog's News tab.

Click to enlarge.

Click to enlarge.

Bristol-Myers, however, has its bases covered with a combination therapy patent that covers PD-1s and other therapeutic compounds and compound categories. Again, Merck challenged it, noting such in the above mentioned quarterly filing:

On April 30, 2014, the Company, and three other companies, opposed another European patent (EP 2 161 336) (“’336”) owned by BMS and Ono that it believes is invalid. The ‘336 patent, if valid, broadly claims anti-PD-1 antibodies that could include pembrolizumab. {Underlined emphasis is mine.}

Bristol-Myers and Ono Pharmaceutical's '878 patent covers PD-1s as monotherapies.

Bristol-Myers and Ono's '336 patent covers PD-1s in combination with other agents, and appears to include a number of companies' products including Amgen's oncolytic virus and intralesional agent talimogene laherparepvec ("T-Vec"). T-Vec had been combined with Bristol-Myer's approved [anti-]CTLA-4 agent ipilimumab (trade name Yervoy), the results of which were presented at ASCO 2014. Amgen and Merck plan to combine T-Vec with Keytruda in a trial slated to start later this year.

A Big Pharma (BMS) with a market capitalization of about $85 billion (per Yahoo! Finance as of yesterday's close) battling one (MRK) with a market cap of about $176 billion. Afterall, in 2013, Citi analyst Andrew Baum estimated potential annual immuno-oncology-related sales to be $35 billion by 2023 (cough). Titans battling...

It does not appear PV-10 is covered by Bristol-Myers and Ono Pharmaceutical's '336 combination therapy patent. PD-1s in combination with PV-10 apparently are, however, covered by Provectus' combination therapy patent application (20120263677 ["'677"]) that it jointly filed with Pfizer (through an expansion, or continuation in part, of Claim #1) in 2012. Pfizer and Provectus would share CTLA-4-related combination therapy sales revenue via the '667 patent application if/when issued, but the former has no claim in the patent app on economics derived from PD-1-related combination therapy sales.

Whether the '878 monotherapy patent ultimately prevails -- that is, whether Merck is violating the patent for tackling cancer (see paragraph 047) -- is Merck's problem, and the Big Pharma eventually may elect to direct royalties Bristol-Myers and Ono's way(s).

Merck could, however, circumvent paying the other parties by meaningfully combining pembrolizumab/Keytruda with PV-10. Directionally speaking, immuno oncology is trending towards combination therapies for late-stage cancer treatment. Strategically, PV-10 should permit Merck's PD-1 to achieve greater tumor destruction and immunological signaling, and be the perfect front end for an immunologic back-end like Keytruda for the ultimate and better benefit of patients than what the PD-1 alone could achieve as a monotherapy. This combination proposition of course would require a sound scientific and medical data-based foundation, which one hopes Moffitt Cancer Center will present and convey at the Society for the Immunotherapy of Cancer's annual meeting in early-November. Tactically, an effective Keytruda/PV-10 combination with a compelling clinical value proposition should obviate the need for royalty payments to Bristol-Myers/Ono because the '336 combination patent would not be infringed. Increasing anti-PD-1 antibody patent opposition and litigation could tip Merck's decision-making scales in favor of embarking on a near-term combination study of Keytruda and PV-10, with perhaps an eye to a longer-term combination.

What It Means for $MRK to be a Dark Horse for $PVCT

Dr. Perlmutter was responsible for Amgen's acquisition of BioVex and its principal drug compound OncoVEX, now T-Vec (talimogene laherparepvec). T-Vec is a competitor of PV-10.

Perlmutter now runs Merck's R&D organization. Merck's licensing group/function now reports to him, and Dr. Perlmutter is keenly interested in business development and licensing.

Thank you to the blog reader who indicated the prior $MRK posts were hazy in their implication.

Implication: Merck may well be a serious contender [to Pfizer] to license PV-10.

$PVCT: More $MRK's Perlmutter

A Dark Horse For $PVCT: $MRK

As global Big Pharma interest in the company accelerates, Merck is a dark horse for Provectus.

Article link here.

Article link here.

Article link here.

$PFE, $MRK: When you can't drive top line, continue to financially engineer the bottom line

May 22, 2013: "Pfizer said that selling the rest of Zoetis will boost earnings starting in 2014...In April 2012 Pfizer sold its infant nutrition business to Nestle SA for $11.9 billion. The drugmaker has said it plans to use cash from asset sales to aggressively buy back its shares. Last month Pfizer said it had repurchased $6.3 billion of stock this year and was authorized to spend another $5.5 billion on buybacks."

May 22, 2013: "Under the accelerated share repurchase agreement (ASR), Merck has agreed to repurchase about 99.5 million shares from Goldman Sachs based on current market prices. "We don't have consensus share count post-Q1 earnings to quantify the impact of the accelerated repurchase, but we believe this is a positive sign of Merck attempting to create shareholder value," ISI Group analyst Mark Schoenebaum said in a note to clients. Merck's board had authorized additional purchases of up to $15 billion of its common stock and said that it would buy back about $7.5 billion over the next 12 months. Sales of Merck's asthma drug Singulair plunged 75 percent to $337 million in the first quarter. The pill was Merck's biggest product, with annual sales of $6 billion, before cheaper generics flooded the U.S. market last August. More pain from generics is in store. Merck's Maxalt migraine drug recently lost patent protection and its Temodar brain cancer medicine will soon face cheaper copycats."

@Bloomberg @BloombergNews: Human Immune-Boosting Cancer Drugs Seen Extending Lives

An article by Robert Langreth here (May 12, 2013).

"Merck & Co. (MRK), Bristol-Myers Squibb Co. (BMY) and Roche Holding AG (ROG) have opened a new front against cancer with the next generation of experimental drugs that use the human immune system to seek and destroy tumor cells."

"Building on the success of Bristol-Myers’ Yervoy drug for melanoma that reached the market in 2011, drugmakers are devising more potent immune therapies or combining treatments for maximum effectiveness. They are also testing the new medicines in more types of cancers, including lung and breast."

"If the new generation of immune therapies lives up to its promise, “this is going to be a paradigm shift for treating cancer,” said Merck senior vice president Gary Gilliland in an interview. “We are pretty good at shrinking tumors, but not good at getting rid of them. Immune therapy is a way to begin to approach that.”"

"Now many believe that by strengthening the immune system’s ability to identify and kill cancer cells, they can broaden the attack so it will fight any dangerous malignancy. “You’re setting up a fair fight” with the disease, said Nils Lonberg, a senior vice president at Bristol-Myers, in a telephone interview. “The immune system is just as adaptable as the cancer.”"

"Cancer doctors “are accustomed to moving from one therapy to another” as tumors rapidly develop resistance,” he said in a telephone interview. “It is generating tremendous excitement to have a drug class that might well be able to provide long term control of metastatic cancer.”"