November 2013 – Maui Derm

Immunodermatology: Part 2: Practical Immunology

November 30, 2013

Andrew Blauvelt, MD, MBA

Practical immunology is important for dermatologists to understand as it relates to a wide variety of pipeline drugs currently under investigation. In Dr Blauvelt’s view, there are three major cell types involved in psoriasis pathogenesis: 1) dendritic cells (upstream/initiating immune responses); 2) T cells (making pro-inflammatory cytokines); and 3) keratinocytes. Targeting IL-23, which is made by dendritic cells, leads to reductions in Th17 cells, since IL-23 is the major survival and growth factor for this type of T cell. Thus, ustekinumab is an indirect T-cell targeting agent. The main cytokine that is being made by the Th17 cells is IL-17A, which leads to activation and growth of keratinocytes. IL-17A is now considered the main effector cytokine of psoriasis. So, by targeting IL-17, downstream function of keratinocytes can be normalized.

A recent study looked at patients on either etanercept or ixekizumab (an anti IL-17A antibody currently under investigation for the treatment of psoriasis). Within two weeks of initiation of therapy, ixekizumab led to the down-modulation of psoriasis-related gene expression to a much greater extent when compared to etanercept. Of the 959 genes up-regulated with psoriasis, 559 were turned off within two weeks of ixekizumab therapy versus 84 with etanercept therapy. This proof-of-concept translational study supports the idea that IL-17A is a key cytokine involved in the pathogenesis of psoriasis.

Pipeline products that specifically block IL-23

These products are unlike ustekinumab in that they do not block IL-12.

MK-3222, an anti-p19 monoclonal antibody (mAb), from Merck
- Phase 3 studies underway
CNTO1959, an anti-p19 mAb, from Janssen
- Phase 2 studies completed
AMG139, an anti-p19 mAb, from Amgen
- Phase 1 studies completed

Pipeline products that block IL-17A function

Secukinumab, a fully human anti-IL-17A mAb, from Novartis
- In Phase 3 studies, phase 2 studies published in 2012 (Br J Dermatol)
Ixekizumab, a humanized anti-IL-17A mAb, from Lilly
- In Phase 3 studies, phase 2 studies published in 2012 (N Engl J Med)
Brodalumab, a fully human anti-IL-17RA receptor mAb, from Amgen
- In Phase 3, phase 2 studies published in 2012 (N Engl J Med)

According to Dr. Blauvelt, all three of the IL-17 blockers look incredibly good from published results and the safety signals, thus far, also look good. If Phase 3 studies confirm these initial results, clinicians will soon have a variety of new promising agents to treat psoriasis patients.

Acquired T-cell Immunity

Regarding the normal function of Th17 cells, individuals who have impaired Th17 responses develop chronic mucocutaneous infections, especially with Candida albicans and Staphylococcus aureus (e.g., Job’s syndrome); these patients also do not develop psoriasis. Normal Th17 responses lead to healing of acute infections with these organisms and no psoriasis (e.g., healthy individuals). Exaggerated Th17 responses lead to healing of acute infections, but eventual development of psoriasis. Of importance, the IL-23/Th17 pathway seems to be less important to systemic immunity when compared to skin and mucosal immunity.

Interestingly, there is also emerging literature regarding the role of IL-17A in the pathogenesis of atherosclerosis. This may mean that targeting of IL-17A may not only treat psoriasis, but also improve atherosclerosis. This, in turn, may decrease the risk of cardiovascular disease associated with psoriasis.

Looking into the Future

As dermatologists, it is important to consider whether drugs that inhibit IL-23 or IL-17 cause or worsen skin or mucosal infections, such as those caused by S. aureus and Candida. Based upon the normal function of this immune pathway, it is unlikely that these drugs will cause or worsen systemic infections. Lastly, it remains to be determined whether they will impact systemic anti-inflammatory activity, including atherosclerosis. Obviously, this latter point will be very important when choosing the proper therapy for patients with moderate-to-severe psoriasis.

Immunodermatology: Part 1

November 30, 2013

Andrew Blauvelt, MD, MBA

Immunodermatology is an important content area for dermatologists to consider when managing patients with psoriasis. The genetics of psoriasis has been an exciting and complex area of research over the last few years, especially in terms of how genetics relate to the immunology of psoriasis. A recent paper highlighted how psoriasis genetics and pathogenesis are much more complicated than was formerly believed. Previously, there were 26 identified genetic susceptibility loci associated with psoriasis risk, and now there have been an additional 15 loci identified. Dr. Blauvelt, when discussing psoriasis with his patients, describes it as a complex polygenic disease; yet, according to Dr. Blauvelt, up to 60% of psoriasis patients will have no other family members with the disease. According to the paper, investigators are “just scratching the surface” and these 41 genetic signals account for approximately 22 percent of estimated psoriasis heritability and further genetic studies, including fine-mapping studies and searches for uncommon susceptibility variants, are in order (Tsoi LC, et al. Identification of 15 new psoriasis susceptibility loci highlights the role of innate immunity. Nat Genet. 2012;44(12):1341-1348).

It is also important to consider the overlap between psoriasis genes and susceptibility genes identified for other autoimmune diseases, such as Crohn’s disease, ulcerative colitis, celiac disease, ankylosing spondylitis, rheumatoid arthritis, systemic lupus, multiple sclerosis, and types 1 and 2 diabetes. All of these diseases are polygenic (numerous genes are contributing to the susceptibility), which is a common theme of many common diseases. Of particular interest is the fact that 11 out of 41 susceptibility genes overlap between psoriasis and Crohn’s disease; in fact, six of the 11 genes are related to the IL-23/Th17 cell signaling pathway, suggesting that Crohn’s disease may respond to IL-23/Th17 blockade.

Psoriasis genes fall into five major functional categories and are either related to the innate or acquired immune system. These categories include genes linked with IL-23/Th17 cell activation (acquired); antigen presentation (acquired); type 1 interferon induction (innate); NF-kB signaling (innate); and skin barrier function (innate). Genes that are psoriasis-specific, i.e., no other disease associations, are mostly associated with innate immunity.

Examples

IL-36

The genetic basis for generalized pustular psoriasis has been identified. Mutations occur in the gene that encodes for the IL-36 receptor antagonist. This is an example of classic Mendelian inheritance, in that patients who have mutations in this gene develop disease; if they do not have defects, then they do not have the disease. Therapeutically, there is no IL-36 antagonist drug yet, however, this may be developed in the future for patients with generalized pustular psoriasis. IL-36 normally stimulates keratinocytes to produce IL- 8, which is a major neutrophil chemotactic factor. IL-36 will drive neutrophils into the skin, and patients who have this defect in their IL-36 antagonist will have uncontrolled levels of IL-36, leading to elevations in other more downstream pro-inflammatory cytokines (TNF, IL-8, IL-6, IL-1).

CARD14

CARD14 is another example of Mendelian inheritance, being that patients who have critical mutations in this gene develop chronic plaque psoriasis. On chromosome 17, a mutation in Card14 (G to A) at position 349 was seen in certain familial cases of psoriasis. CARD14 mutation is involved in the innate immune system. Dysfunction in this gene leads to increased NF-kB activity; this, in turn, leads to increased pro-inflammatory cytokine production by keratinocytes.

Numerous other CARD14 variations are associated with non-familial cases of psoriasis as well. These variations however, are not Mendelian. The genetic variations translate into increased NF-kB activity in keratinocytes and increased risk to develop psoriasis.

IL23R

Dr. Blauvelt notes that this gene is very clinically relevant as it relates to the mechanism of action of ustekinumab. The IL23R R381Q gene variant protects against immune-mediated diseases by impairing IL-23-induced Th17 effector response in humans. If patients don’t have fully functional IL-23 receptor, then IL-23 does not function well as a stimulator of Th17 cells; thus, this gene defect protects against psoriasis development. This is a genetic “hit” to the system, whereas ustekinumab would be a pharmacologic “hit” to the system.

Other genes associated with the IL-23/Th17 pathway include the p19 subunit and the p40 subunit of IL-23 itself.

Summary

There is a tremendous amount of new information regarding genes and psoriasis. Psoriasis pathogenesis represents a complex interplay between innate (how the skin initially reacts) and acquired immunity (mostly related to the IL-23/Th17 pathway). There is certainly a lot more detailed research to come in this area. Regarding translating this information to the bedside, the hope is that genetic profiling will help clinicians predict severity and course of disease as well as to help determine the response to specific therapeutic agents.

Small Molecules for Psoriasis: A New Frontier?

November 27, 2013

Kenneth Gordon, MD

Small molecules were the mainstay for systemic psoriasis therapy for about forty years. Many patients would say that they prefer small molecules, i.e., a pill to a shot and, in fact, sometimes physicians feel more comfortable with a pill as well. In the last decade; however, all attention with regards to the treatment of psoriasis has been given to the biologics.

How will these small molecules impact the dermatology practice?

Methotrexate (MTX) is the small molecule standard and, for the most part, well-tolerated. Most countries require the use of MTX before trying a more expensive medication. Unfortunately, some of the first studies for MTX were conducted poorly. Overall, you can expect to achieve a PASI 75 of about 40 percent with relatively aggressive MTX dosing when compared to biologics.

Apremilast

Apremilast, an inhibitor of PDE4, is currently under development for the treatment of psoriasis.

In Phase III studies, apremilast (30 mg BID) has achieved a PASI 75 achievement rate of 33%. The majority of adverse events (AEs) were not serious. The phase III results (ESTEEM I and II) demonstrate greater improvements from baseline Dermatology Quality of Life Index versus placebo and a greater proportion of patients reported improvements in the MCID versus placebo. Apremilast seems to be well tolerated in patients with moderate to severe psoriasis, with mild and infrequent gastrointestinal side effects (nausea and diarrhea).

The JAK/STAT Pathway

Tofacitinib, a novel, oral JAK inhibitor recently approved for the treatment of rheumatoid arthritis, is currently being investigated as a treatment for psoriasis among other indications. Although tofacitinib is a small molecule that binds to a specific area, it may have a wide range of effects; therefore, targeting various phases of the inflammatory process.

The phase II data on tofacitinib (15mg BID and 5 mg BID) demonstrate a PASI 75 achievement rate of 67 percent and 40 percent at week twelve, respectively; therefore, showing that this could be quite effective for the management of psoriasis. The issue that we have with this therapy is the overall safety of this medication.

When looking at some of the data that we have in rheumatoid arthritis, we see changes in baseline in hemoglobin and also lymphocyte changes. An FDA briefing document states that as the dose of tofacitinib increases, as does the risk of malignancies, this also seems to be true for lymphoma and infection. While this medication has a broader immunosuppressive effect, there may be more issues with side effects and that is something, as dermatologists, that needs to be considered.

In conclusion, you can see that small molecules are again being developed for systemic psoriasis therapy. While they have exciting mechanisms of action, it remains to be seen if they will be superior to methotrexate in both efficacy and safety, especially with regards to the immune system. Pricing and prior authorization requirements will be critical when it comes to treating patients.

Psoriasis Update 2013: Emerging Therapies

November 27, 2013

Craig Leonardi, MD

It is crucial that dermatologists recognize the major advances in the management of psoriasis. Psoriasis affects approximately one to two percent of the general population in the United States, plaque psoriasis being the most common form accounting for approximately 90 percent of all cases.

It is important to look at where dermatologists have been with the use of biologics over the last decade. The first set of drugs were the T-cell inhibitors. T-cell inhibitors work by blocking T-cell activation; it is a multi-step process. The primary signal was the presentation of antigen; the secondary signal was that of the binding of accessory ligand pairs; therefore, forming immunologic “synapse.” According to Dr Leonardi, this was a wonderful rationale, but since then these drugs have fallen by the wayside for a number of reasons. For example, alefacept (withdrawn from market in 2012) was probably one of the least efficacious drugs approved. Efalizumab had serious infections (i.e., progressive multifocal leucoencephalopathy (PML)) and was taken off the market in 2009. From that point, attention then drifted over to cytokines and cytokine inhibitors for the treatment of chronic inflammation.

The 2^nd generation biologics are what Dr Leonardi characterizes as the TNF-alpha inhibitors. Etanercept, in its usually approved dose of 50 mg once weekly, achieves a 45-50% PASI 75 response and you can see even more improvement with the double dose of 50 mg twice weekly.

Infliximab, three infusions in the first six weeks, will carry patients up to about an 80% PASI 75 achievement rate, and then you will see a slow loss of response over time; however, there will still be about 60% PASI 75 achievement rate over the long term.

Adalimumab achieves a 71% PASI 75 at week 16.

Third generation biologics include ustekinumab and briakinumab (which never completed the FDA-approval process for psoriasis). Phase III data on ustekinumab was positive in both the PHOENIX 1 and PHOENIX 2 studies, and demonstrates that it is a high performance drug blocking IL-12 and IL-23 showing a sustained PASI 75 response of approximately 67-75% (depending on dose) as compared to placebo. Ustekinumab also has a nice, durable effect.

What about breakthrough early on with ustekinumab? In between doses of ustekinumab it’s very common to see patients who have some return of disease prior to their next dose, but Dr Leonardi urges clinicians to encourage patients to continue and hold on to see the positive effects.

Ustekinumab Safety Data

Over time, adverse events on ustekinumab are coming down, infections are low and stable over time, and SAEs that lead to discontinuation seem to be low and stable as well. One caveat to keep in mind is that in any long term analysis like this, patients are coming out of the trial because they either are not responding or are not tolerating the drug well. From this perspective, long-term safety data from open label extension studies usually looks favorable.

New Development Efforts

There are several new drugs currently in development of the treatment of psoriasis. These therapies target IL-23 (without targeting IL-12) and IL-17. Ixekizumab, an IL-17 inhibitor, appears to be a very promising drug in the pipeline with almost 50 percent of patients in the studies achieving a PASI 100. As far as adverse events (AEs) are concerned, there were no serious AEs and this is extremely comforting.

The IL-17 receptor blocker, brodalumab, was studied in a variety of different dosing strategies. Brodalumab showed about an 80 percent PASI 75 achievement rate, demonstrating a very high performance. There were a couple of serious adverse events (four), but they seemed to be unrelated to medication and no serious infections or cancers were reported.

The data on secukinumab, another inhibitor of IL-17, is difficult to explain as the studies are rather disjointed, in that, as a dermatologist, one has to look past the published data. The higher dose of secukinumab (150mg) was selected for the phase III trials because of its PASI 75 response rate of approximately 81%. There were no serious adverse events with secukinumab.

Conclusions

Dermatologists have seen an explosion of biologic drugs that are mostly targeting the IL-17 and IL-23 pathway
There are a variety of novel small molecules that are under investigation
JAK inhibitor may be a new topical approach
Short and long-term safety issues will depend on the results of the ongoing phase III studies and subsequent post-marketing data capture.
Assess benefit/risk ratios when deciding on appropriate treatment strategies