Psoriatic arthritis (PsA) is a chronic autoimmune condition — it causes the immune system to attack joints and, sometimes, other tissues. PsA usually develops in people who already have the skin condition psoriasis.

“As we see newer epidemiology studies, we’re beginning to realize that the disease is more common than we thought, historically,” Dr. Philip Mease, a clinical professor at the University of Washington School of Medicine and the Director of Rheumatology Research at Swedish Medical Center, in Seattle, told Medical News Today.

“Psoriasis is a relatively common condition that occurs in up to about 3% of the population,” he continued, “and we think that PsA then occurs in up to about 30% of those patients.”

A person with PsA may develop inflammation in any joint. The inflammation may also occur where tendons or ligaments attach to bones, an issue that doctors call enthesitis. In addition, PsA can affect the skin, nails, or both.

To help reduce the disease activity and slow the progression of PsA, rheumatologists prescribe medications known as disease-modifying antirheumatic drugs (DMARDs).

Historically, methotrexate was often the DMARD of choice. It is a traditional drug that targets the entire immune system. In recent years, however, biologic DMARDs have played an increasing role in PsA treatment.

Biologics are a type of targeted drug made from genetically engineered proteins. They reduce inflammation by blocking the action of specific proteins or cells in the immune system.

This article provides an overview of the available biologics that can help treat PsA. It also describes the strategies that doctors may use to manage the risk of side effects.

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There are a number of biologics approved to treat PsA.

The Food and Drug Administration (FDA) have approved several biologics to treat PsA. These medications fall into four categories:

  • tumor necrosis factor (TNF) inhibitor
  • interleukin-17 (IL-17) inhibitor
  • interleukin-12/23 (IL-12/23) inhibitor
  • T-cell blocker

A person with PsA may have to try multiple biologics to find the type that works best for them. If one drug is ineffective or causes any disruptive side effects, the doctor may prescribe another type of biologic or a nonbiologic DMARD.

There is no single biologic agent that is best for everyone with PsA,” Dr. Brett Smith — a rheumatologist at Blount Memorial Physicians Group, in Maryville, TN, and the East Tennessee Children’s Hospital, in Knoxville, told MNT.

“I would encourage patients to speak with their rheumatologist about options for treatment and which drugs may be appropriate for them,” Dr. Smith continued.

Compared with conventional DMARDs, biologics are often “far superior,” in terms of reducing inflammation, swelling, and pain, Dr. Smith said. He added that many people find the side effects of biologics to be easier to tolerate than those of methotrexate.

In rare cases, however, biologics can cause severe side effects. Also, because they are relatively new forms of treatment, data regarding the safety of long-term use have been limited.

“We do not have very long-term data yet,” Dr. Rajat Bhatt, a rheumatologist at Prime Rheumatology, in Richmond, TX, explained. “There might be unknown risks.”

For most people with active PsA, TNF inhibitors are the first line of treatment recommended by the American College of Rheumatology and National Psoriasis Foundation.

The FDA have approved the following TNF inhibitors for treating PsA:

  • adalimumab (Humira)
  • certolizumab pegol (Cimzia)
  • etanercept (Enbrel)
  • golimumab (Simponi, Simponi Aria)
  • infliximab (Remicade)

If a person is taking Remicade or Simponia Aria, they will visit their doctor’s office or an infusion clinic to receive the drug by intravenous infusion — an IV.

Other types of TNF inhibitors are injected under the skin.

How they work

In people with PsA, the body produces too much of a protein that drives inflammation — called TNF-alpha — in the skin or joints.

TNF inhibitors help block the production of this protein, which can thereby reduce inflammation.

According to a summary of evidence published in Expert Review of Clinical Pharmacology, clinical trials have shown that all five types of TNF inhibitors can limit the progression of PsA.

Side effects

TNF inhibitors suppress the immune system. As a result, they raise the risk of infection, such as influenza or sinus infection.

Other potential side effects of TNF inhibitors include a rash, headaches, nausea, and pain and swelling at the injection site.

In rare cases, people taking TNF inhibitors have experienced more severe adverse effects, including:

  • serious allergic reactions
  • serious infections
  • liver problems
  • nervous system problems
  • lupus-like syndrome
  • a low blood count
  • lymphoma and other types of cancer
  • heart failure

A doctor may not prescribe a TNF inhibitor to a person with a history of certain medical conditions, including serious or recurrent infections, congestive heart failure, or a demyelinating disease, such as multiple sclerosis — MS.

The American College of Rheumatology and National Psoriasis Foundation recommend IL-17 inhibitors as a second-line treatment for PsA. These drugs may help treat PsA that has not responded well to TNF inhibitors.

In other cases, a doctor may prescribe an IL-17 inhibitor to a person who has a medical condition that would make it less safe to use TNF inhibitors.

To date, the FDA have approved two IL-17 inhibitors for PsA:

  • ixekizumab (Taltz)
  • secukinumab (Cosentyx)

Both of these medications are injected under the skin.

How they work

IL-17 is a type of signaling protein that plays a role in the development of inflammation in PsA.

IL-17 inhibitors interfere with IL-17 signaling. This interrupts the inflammatory processes that are involved in PsA and can thus help relieve its symptoms.

Clinical trials have shown that Cosentyx and Taltz are both very effective at treating PsA, researchers report in Frontiers in Pharmacology.

Side effects

IL-17 inhibitors suppress the immune system and, thus, increase the risk of infections, such as influenza, sinus infections, and fungal infections. Other side effects can include allergic reactions, diarrhea, nausea, and pain and swelling at the injection site.

IL-17 inhibitors may also raise the risk of inflammatory bowel disease (IBD). In people who already have IBD, this type of medication may worsen their symptoms.

An IL-12/23 inhibitor may be effective when PsA has not responded well to TNF inhibitors or IL-17 inhibitors.

Alternately, a doctor may prescribe an IL-12/23 inhibitor if a person has both PsA and IBD.

The FDA have approved one type of IL-12/23 inhibitor to treat PsA: ustekinumab (Stelara).

The drug is injected under the skin.

How it works

IL-12 and IL-23 are two types of protein involved in the development of inflammation. Stelara blocks IL-12 and IL-23, which can help reduce inflammation and minimize symptoms.

Side effects

Like other types of biologics, Stelara suppresses the immune system and raises the risk of infection. Other common side effects of Stelara include headache and fatigue.

In rare cases, this medication has been associated with serious infections and types of cancer. In addition, one person taking the medication developed a very rare neurological condition called reversible posterior leukoencephalopathy syndrome.

If PsA has not responded well to other biologics, the doctor may prescribe a type of T-cell receptor blocker called abatacept (Orencia).

This medication may be administered through an intravenous infusion, or it may be injected under the skin.

How it works

Orencia hinders the activation of T-cells, a type of white blood cell that helps drive inflammatory processes in PsA. By inhibiting the activation of T-cells, this drug can help reduce inflammation and relieve symptoms of PsA.

A review published in Psoriasis: Targets and Therapy found that Orencia can treat PsA but not skin psoriasis.

Side effects

Like all biologics, Orencia raises the risk of infection, such as influenza, sinus infections, and upper respiratory infections. Other common side effects include headaches and nausea.

In rare cases, Orencia may trigger a serious allergic reaction.

Biosimilars are drugs developed to be very similar to biologics that have already been approved for use.

The FDA have approved several biosimilars for the treatment of PsA, including:

  • adalimumab-atto (Amjevita) and adalimumab-adbm (Cyltezo), which are biosimilar to Humira
  • etanercept-szzs (Erelzi), which is biosimilar to Enbrel
  • infliximab-dyyb (Inflectra) and infliximab-abda (Renflexis), which are biosimilar to Remicade

Before the FDA approves a biosimilar for use, the manufacturer must show that it is nearly identical to the original biologic at a molecular level.

The manufacturer must also show that it has comparable efficacy and safety when treating one of the conditions that the original biologic been approved to treat.

If the biosimilar meets those criteria, the FDA will approve its use as a treatment for every condition that the original biologic has received approval to treat.

This means that biosimilars are approved treatments for a range of conditions, even when no studies have investigated some of these applications. As a result, some rheumatologists are wary about prescribing them.

“That scares many rheumatologists because we do not know whether it is going to be efficacious or not in the scenarios where it has not been tested,” Dr. Shailendra Singh — the Rheumatology Medical Director of White River Medical Center, who works at the center’s specialized clinic in Batesville, AR — told MNT.

However, other rheumatologists are more comfortable prescribing FDA-approved biosimilars.

“My opinion, based on looking at lots of data from the various biosimilar trials for infliximab, adalimumab, and so forth, is that all of the reputable companies are making extremely good copies of the originator,” Dr. Mease told MNT.

“And so, I personally have not had virtually any qualms about the true biosimilarity of these molecules,” he explained.

When a doctor prescribes a biosimilar instead of an original biologic, it can save costs for the person and the healthcare system because biosimilars tend to be less expensive.

In many people, biologics help reduce inflammation, swelling, pain, and other symptoms of PsA. They may also help slow the development of the disease and limit joint damage.

However, biologics can cause side effects, which in rare cases are serious. Doctors should monitor people who are taking biologics for signs of infection and other side effects.

To learn more about the potential benefits and risks of taking a biologic, speak with a rheumatologist.

“I’m always open to any questions my patients have,” Dr. Singh told MNT.

I usually give them information with all the possible side effects of the medication,” he continued, “and I’ll say to them, ‘Read it, and then we’ll sit down and discuss each and every point and any concerns that you have.’”