Our Body's Defenses
A product of millions of years of evolution, the human immune system is a complex group of defense mechanisms that the body uses to protect itself from foreign invaders, such as germs, viruses, and toxins. The skin which serves as a physical barrier against these potentially dangerous invaders is one element of the immune system. Other reflexes, such as sneezing and coughing, are common behaviors that serve to discard foreign particles that may enter our body when we breathe.

A variety of immune cells provide defenses against unwanted intruders (which are called pathogens because they are able to disrupt the body’s regular activities and cause disease). There are surveillance cells that detect the presence of foreign invaders and others that attack them. Still other cells learn to identify and remember foreign invaders that have escaped detection and caused damage, so that the immune system can spring into action the next time that specific invader appears. All of these cells work together, sending signals back and forth to one another when a threat is present and action is required to isolate and attack the foreigner.

In addition to their role in fending off foreign invaders, immune cells also participate in the process of eliminating the body’s own cells that fail to function properly or those that die after living out their normal cycle.

Detecting Threats
To function properly, the immune system relies on its ability to distinguish between “self” and “non-self.” If these distinctions could not be made, the immune system would attack normal cells, thereby causing damage to otherwise healthy tissue. However, normal cells in every individual contain a unique set of markers on their surfaces, which designate them as “self” and thus avoid attack by the immune cells. This is known as self-tolerance.

In contrast, foreign invaders, diseased and damaged cells have different markers on their surfaces that enable immune cells to distinguish them as “non-self,” and to mount a response to target and eliminate them. The markers that trigger the immune response are called antigens. When “self” cells are infected by pathogens, they will produce antigens as well, thereby signaling the immune system to attack.

This ability to distinguish between normal cells, irregular cells, and foreign invaders is a product of two different response systems. Our innate immunity allows us to recognize and attack foreign invaders the very first time they are present. The knowledge about these invaders’ danger is quite literally coded in our genes at birth. In developmental terms, innate immunity is a much older system, derived from the defense mechanisms of some of the earliest forms of life.

Acquired immunity—also known as adaptive or specific immunity—is a learned process that enables the body to remember specific foreign invaders that may have evaded the innate immune defenses. Acquired immunity provides long-term protection against particular pathogens. Acquired immunity is why prophylactic vaccines are administered against a number of diseases (e.g., polio, diphtheria, influenza, etc.). The vaccine often contains an inactive form of the invader, which can’t cause an infection, but nevertheless introduces the antigen to the immune system so that it will be ready the next time it confronts the invader in a more dangerous form.

In response to an antigen, the immune system goes through a series of activities to detect, isolate, destroy, and then remove the foreign substance. A number of specialized cells are summoned that initiate and coordinate the response and subsequently, several different methods of disposing of the invader or damaged cell can be activated. In some cases, immune cells engulf and swallow the foreign invader whole, a process called phagocytosis (“phago” means “eat”, “cyto” refers to cells). Other immune cells kill “non-self” or diseased cells by injecting them with harmful substances.

In other cases, immune cells produce proteins known as antibodies, which latch on directly to the antigen at the surface of the cell, much like a key fits into a lock. Antibodies are specific to a particular antigen, and when an antibody locks onto its antigen, the combined structure is called an antigen-antibody complex; these complexes enable other immune cells which have the ability to kill.

When the immune response involves antibodies, it is called humoral immunity, because these antibodies circulate throughout the blood stream. Cellular immunity refers to the activities of the immune system that involve white blood cells and not antibodies.

Our Body's Defenders
The immune system’s foot-soldiers include different white blood cells that circulate throughout the body or reside in tissues. These cells play different functions in response to the presence of antigens. Important types of white blood cells include neutrophils, lymphocytes, monocytes, and dendritic cells, all of which are produced by bone marrow.

Neutrophils are the most common form of white blood cell. Their function is to kill invading bacteria, by swallowing them and then destroying them with chemicals they release. Neutrophils have a very short life—less than 10 hours once they are activated—and are most often involved in the initial response to combat foreign invaders.

Another group of white blood cells known as lymphocytes can survive for decades. They undergo a process of education and maturation that prepare them for their specific functions. The vast majority of the body’s lymphocytes (80 percent) travel from the bone marrow to the thymus, where they receive specialized capabilities to recognize foreign antigens and, in some cases, the mechanisms to destroy them.

Lymphocytes that are processed in the thymus are called T cells, and among T cells there are different specialists. T cells called killer T cells, destroy cells that have been infected by viruses and bacteria; they also help eliminate cancer cells that have not yet adapted to evade the immune system. Other T cells, serve as memory cells that “remember” antigens after only one encounter, and sound the alert for other immune cells to respond when they recognize a foreign invader. T cells called helper T cells produce various cytokines (see below) some of which regulate antibody production. Regulatory T cells (T regs), also known as suppressor T cells, work to turn off the immune response and play an important role in maintaining self-tolerance. T cells are differentiated by a group of structures on their surfaces, which give rise to the identification of T cells by their “CD” (cluster-determined) labels as CD3, CD4, etc. T cells are the primary cells involved in cellular immunity.

B cells are lymphocytes that mature in the bone marrow, and B cells produce the antibodies that attach to antigens. B cells usually produce antibodies in response to an activation signal from a T cell, but they can also produce antibodies on their own as a direct response to antigens. Some B cells also serve as memory cells, surviving for years. B cells are the primary cells involved in humoral immunity.

There are millions of B cells and T cells circulating in the body at any given time, with a relative few armed to detect a specific antigen. Once that antigen is encountered, however, these particular cells are recruited and multiply profusely, creating a massive army to confront the invader. This process of rapid cellular reproduction is called clonal expansion; the cells that are armed to do battle are said to be immune competent. Once the infection or invader is contained, the armed lymphocytes die at the end of their natural life cycle.

Natural killer (NK) cells are another form of lymphocyte, which are physically much larger than B cells or T cells. NK cells are part of the innate immune response. They attack viruses and tumor cells, and work by injecting small granules into cells that kill them.

In addition to lymphocytes, another type of white blood cell called monocytes play important roles in the immune response. Monocytes are large cells that circulate in the blood or reside in tissue in search of foreign invaders, diseased cells, dead cells, or cellular debris. Monocytes that reside in tissue are called macrophages. The macrophage works by swallowing its intended target. When a macrophage does encounter a potential target, any one of several responses may occur. The macrophage can attack the antigen or diseased cell directly, swallowing it and carrying it away. In other instances, the macrophage may act by presenting the antigen to the T cells, which in turn may activate B cell antibody production. Macrophages are then summoned to engulf the antibody complexes and transport them to the spleen for removal from the body. Finally, macrophages can also release substances that contribute to the immune response.

Dendritic cells are another type of immune cell which earned their name from the spiky projections that develop as they mature. Dendritic cells’ primary function is to locate and capture antigens, and then present them to T cells. On their own, T cells do not react to antigens that they have not encountered before. They must first have an unknown antigen presented to them by other cells. Because of this activity, dendritic cells are classified as a type of antigen presenting cells (APCs).

Immature dendritic cells leave the bone marrow and circulate in the blood and through tissue in search of antigens. Once they encounter an antigen, the immature dendritic cells begin their maturation process, which involves attacking and capturing the antigen, and transporting it to the lymph nodes. There, in the lymph node, the mature dendritic cells will present the antigen to T cells, initiating rapid reproduction of millions of helper, killer, and memory T cells dedicated to finding and eradicating that antigen. Dendritic cells are the most powerful APCs and are key cells in the body’s defenses against cancer.

In both their surveillance and combat roles, B cells draw upon a number of complement chemicals and proteins to aid the process. Complement proteins are produced in the liver. They can attach themselves to foreign invaders and kill them. Complement proteins also can attach themselves to immune complexes which facilitates their elimination. Their work in support of other elements of the immune system is why these compounds are called “complement.”

The Chemical Messengers
Cytokines are chemical messengers produced by lymphocytes and macrophages. They can affect nearby cells or those more distant. Macrophages release certain cytokines to summon T cells. Each cytokine has a specific receptor or set of receptors it binds with on the cell surface. Their functions include promoting cell growth, initiating cellular activity, and killing targeted cells. Interleukins, interferon, and growth factors are all cytokines. Interleukins are referred to by their abbreviation, IL, along with a number that indicates the order in which they were discovered (i.e., IL-1, IL-2, IL-3, etc.). Certain interferon types are thought to help the body attack cancer cells. There is also a cytokine called tumor necrosis factor, which may cause some cancer cells to die.

Helper T cells are classified by the types of cytokines they produce. Th1 cells produce interferon gamma, IL-2, and tumor necrosis factor; Th1 cells promote the cellular immune response. Th2 cells produce other interleukins involved in antibody responses.

A cascade of cellular and chemical activity caused by an effective immune response results in inflammation, a reaction characterized by an increase in blood flow to the targeted tissue or damaged cells, elevated temperature and swelling in the area of activity. Though initiated in order to fend off foreign invaders, inflammation—from the Latin word for “set on fire” —also damages surrounding healthy tissue and is experienced as pain, heat, fever, swelling, redness, and loss of function.

Inflammation can be acute or chronic, and can occur in almost any tissue or organ. Prostaglandins and leukotrienes are chemicals that promote inflammation, as are cytokines produced by certain T cells. Other T cells, however, produce cytokines that actually work to limit inflammation.

Cells Gone Haywire
With few notable exceptions, the cells in our tissues undergo steady and regular replacement, with new cells replacing older cells that have completed their life cycle. This process of cellular replenishment is maintained by a number of safeguards to make sure that the system stays in balance, and that the number of new cells and those that die off remain equal. Apoptosis, which is a form of programmed cell-death, is one such mechanism.

This balance can be disrupted, however, and the number of new cells can rapidly outpace those that are being discarded. Some forms of this accelerated cell growth are not harmful—skin calluses, for example, or the kinds of growths that are referred to as benign tumors.

Cancer, on the other hand, is a form of uncontrolled cell growth that can cause serious damage throughout the body. Cancer cells replicate at a highly accelerated rate, and often disable the mechanisms by which older cells are made to die off. The uncontrolled growth of cancer cells is accompanied by changes that enable them to form a tumor, reorganize the surrounding blood vessels to create their own blood supply, overwhelm neighboring tissues, and invade even distant tissues through the process of metastasis—when cells from a tumor break off and travel through the blood stream and take up residence and begin growing in other parts of the body. As tumors grow, they siphon off nutrients, depriving healthy cells of the basics needed to function and survive.

The Immune Cells' Attack
The interplay between the immune system and cancer cells is complex. Cancer cells originate as “self” but as they convert from normal cells into cancer cells, they develop new and different antigens on their cell surface. These antigens can trigger immune cell activity, and indeed, the immune system is engaged in detecting and eliminating cancer cells all the time. It is estimated that thousands of these abnormal cells are discovered and eliminated every day in healthy people. These activities kill cancer cells and help prevent tumor growth.

At work are the same immune foot-soldiers that work against foreign invaders. Natural killer cells patrol and attack tumor cells by injecting granules of lethal chemicals into the cancer cell which kill it. Killer T cells also target tumor cells, but unlike the NK cells of innate immunity, killer T cells must first be introduced to the tumor antigen by an antigen-presenting dendritic cell. Production of these cancer-killing cells is enhanced by certain cytokines. As with foreign invaders, immature dendritic cells that encounter a cancer cell capture and break off pieces of the tumor antigen, which they then carry off to the lymph node to educate and arm T cells. The immune system also creates antibodies against tumor antigens, but it is not clear antibodies play a major role in combating tumor cells.

The Cancer's Counterattack
Despite the array of forces against them, cancer cells often survive and multiply, in part because tumors have clever defenses as well. In fact, cancer cells have a variety of ways in which they trick or even hijack the immune system to fend off attack. Cancer cells can disguise their antigens to escape detection. Cancer cells can also halt the development of immature dendritic cells that capture cancer antigens; the dendritic cells carry the antigen to the lymph nodes, but fail to mature into antigen presenting cells and thus can not educate and enlist the forces of T cells to kill the tumor cells. Scientists have discovered that tumors also can stimulate production of T reg cells, which suppress the immune response, in part by surrounding themselves with T reg cells, almost like a shield, to keep the body’s killer cells at bay. Tumors can also send signals that trigger apoptosis in immune cells, killing them off in waves of cellular suicide. Anergy is the term used to describe the situation when T cells are unable to mount a proper response.

What determines whether the immune system or the cancer prevails is a mystery. However, it is believed that the greater the number of immune cells that can penetrate and infiltrate the tumor, the better the prognosis. For this and other reasons, scientists and medical researchers have begun to look at reinforcing and recruiting the immune system as a way to improve cancer treatment, a concept called immunotherapy.

It is also generally accepted that a depressed immune system, which has been compromised by illness or poor nutrition, is less able to mount a rigorous defense against cancer cells and the potent diversionary tactics the tumor has at its disposal.

One cancer in which a weakened immune system appears to play a role is squamous cell carcinoma of the head and neck (H&NSCC). Squamous cells are flat cells that cover the surfaces of organs and body parts, including the outside of the tongue, gums, inside of the cheeks and mouth, and the lining of the throat and esophagus. A cancer that develops in these kinds of cells is called a carcinoma.

Some H&NSCC patients have been found to have defects in their immune systems at the time of their cancer diagnosis. Part of this suppression of the immune system stems from poor nutrition, most notably zinc deficiency; zinc supports the thymus and the growth of
T cells, so it is understandable why a lack of zinc can affect the immune system.

A Crafty Foe
In addition, H&NSCC tumors can produce a number of substances that derail the normal activities of immune cells. They produce interleukin-10 (IL-10), a cytokine that works to limit the production of Th1 cells, and transforming growth factor beta (TGF-B), which works to paralyze immune cells. H&NSCC tumor cells also cause prostaglandins to be released, inhibiting T cell response. When dendritic cells capture H&NSCC tumor antigens, factors secreted by the tumor are able to disrupt dendritic cells, preventing them from maturing and presenting antigen to T cells. And it appears that when antibodies lock on to tumor antigens, the resulting antibody complexes work to suppress T cells and to neutralize monocytes.

As a result of all these factors, the immune profile of some H&NSCC patients is generally characterized by reduced number of killer T cells, an increased number of suppressor T cells, dysfunctional dendritic cells, and defective monocytes.

Like all cancers, H&NSCC tumors are classified by their size (or “Stage”) and the degree to which they have metastasized to the lymph nodes, and whether they have migrated to other tissues. Stages I and II refer to smaller tumors, with no apparent metastases. Stages III and IV cancers are more serious, and describe larger tumors that have spread to the lymph nodes. Stage I and II H&NSCC is usually treated by surgical removal of the tumor or by radiation therapy to destroy the tumor. Usually patients with Stage I or II H&NSCC who undergo one of these treatments have good results. For Stages III and IV, patients usually receive both surgery and radiation therapy and even with this combined treatment, the outcomes are not nearly as successful as for earlier stage patients.

IRX-2
IRX Therapeutics has developed a novel agent, IRX-2, that is designed to restore cellular immunity. It has already been in human clinical studies (Phase 1 and Phase 2). It is currently being studied to see if it can improve the outcomes of H&NSCC patients who undergo surgery (“neoadjuvant therapy”).

The design of IRX-2 is an attempt to counteract many of the measures H&NSCC tumors use to disrupt the immune system. IRX-2 is made up of several cytokines—of which the primary active components are interleukin 1 beta (IL-1ß), interleukin 2 (IL-2), interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α). These cytokines promote T cell development, stimulate dendritic cell maturation, and enhance monocyte function. The objective is to restore the patient’s robust immune attack with increased penetration of the tumor by lymphocytes which can lead to tumor destruction. It also may lead to the development of memory T cells that will remember the tumor antigens and initiate an immune response if future tumor cells reemerge.

The IRX-2 Regimen
Patients in the investigational arm of the upcoming INSPIRE trial will also receive several other medications and nutritional supplements, which are intended to create a favorable environment for IRX-2 to work. Together the combination of IRX-2, cyclophosphamide, indomethacin, and zinc (as part of a multivitamin) make up the IRX-2 regimen.

Each of the components of the IRX-2 regimen plays an important role. Cyclophosphamide is a drug that is often used as a chemotherapy agent in cancer treatment; however, in this clinical trial, only a single, low dose is given. This one-time, low dose of cyclophosphamide is intended to reduce the number and function of suppressor T cells (T regs) that help protect the cancer cells. Patients in the clinical trial will receive the cyclophosphamide in the form of an intravenous infusion, which is a timed-release liquid drip into a tube that has been inserted into a vein. The cyclophosphamide infusion takes about thirty minutes and occurs three days before the patient receives the initial treatment of IRX-2.

Indomethacin is a non-steroidal anti-inflammatory drug (NSAID), which limits the production of prostaglandins. H&N SCC tumors produce prostaglandins which inhibit T cells. It is hoped that the use of indomethacin as part of the IRX-2 regimen will also contribute to keeping suppressor monocytes in check. Because indomethacin can create gastritis (irritation) and other stomach problems, patients will also be given omeprazole (or another similar drug) to prevent the irritation. However, the medicine taken to counteract the side-effects of indomethacin is technically not part of the IRX-2 regimen.

Zinc is included as part of the IRX-2 regimen because it is known to be important in maintaining the working of the thymus, where T cells mature. Also, H&NSCC patients frequently have poor nutrition and zinc deficiency.

Both the zinc and the indomethacin are taken orally every day for three weeks, beginning on the same day the patient receives the infusion of cyclophosphamide.

IRX-2 Treatment
Patients in the Investigational arm of the trial will receive IRX-2 over a two-week period. The IRX-2 is given in the form of two injections just under the skin daily, one on each side of the neck just beneath the hairline. Overall, patients will receive 20 injections—2 injections daily for 10 days. The needles used are small, and the shots are usually not painful although skin reactions have been observed to the IRX-2 therapy.

IRX Therapeutics is preparing the launch of its pivotal IRX-2 Phase 3 clinical trial, the INSPIRE trial – IRX-2 Neoadjuvant Therapy in Head and Neck SCC to Provide Immune
Response Enhancement. The INSPIRE trial is only for patients with advanced H&NSCC, whose tumors can be surgically removed. It is hoped that the IRX-2 regimen may be able to immunize the patient against their tumor and thereby prevent or delay recurrence of the cancer after surgery.

The INSPIRE trial will include up to 120 cancer centers in the United States and a number of countries abroad. A total of approximately 500 patients will be enrolled. The INSPIRE trial follows Phase 1 and 2 trials of the IRX-2 regimen. It is hoped that the INSPIRE trial will demonstrate a survival advantage for patients treated with the IRX-2 regimen.