Genetic testing to determine drug suitability

@mtr2601, I've had genetic testing done but not for autoimmune drug therapies. There have been many discussions and comments about genetic testing for various conditions that might be helpful to scan through while you wait for members with experience to respond. Here are the search results for "genetic testing" that shows discussions, comments and more that might be helpful:
https://connect.mayoclinic.org/search/?search=genetic+testing

Genetic testing has potential for diagnostic purposes, prognostic purposes and therapeutic purposes.

I'm not sure what advances are being made across the spectrum of all autoimmune disorders. I doubt much progress has been made for PMR/GCA. The treatment is still prednisone and nothing much has changed since this abstract was written in 1983.
https://pubmed.ncbi.nlm.nih.gov/6882032/
Pathetic progress, if you ask me.

Some autoimmune disorders have known "genetic links." I had a genetic test done over 30 years ago that said I was "predisposed" to a certain type of autoimmune disorder. It was interesting information but not very useful for altering the course of my autoimmune disorder.

The genetic test wasn't at all useful for therapeutic reasons. Treatment for most autoimmune disorders is still a "trial and error" approach.

People with PMR/GCA have precious few treatment options besides prednisone. My rheumatologist said he made a "lucky guess" when he found a biologic that worked for me. I give him more credit than that ... it was at least an "educated guess."

I discovered today that Sonic Laboratories (one of Australia's largest pathology labs) can reliably screen for genetic markers to inform response to Leflunomide. Here the test is not covered by our Medicare insurance and costs $197. This is the next drug my Rheumatologist wants to try if Mtx is not successful. The laboratory does not test for response to Methotrexate, Prednisone or Tocilizimab. I will happily pay for this test before submitting to more 'trial and error ' drugs that could have dire consequences. I agree, the situation for PMR sufferers is quite dire and i wonder if there any organizations lobbying for clinical trials and better access to safer and more effective treatments.

Thanks John, i am finding this Mayo Clinic forum very helpful in so many ways. It has led me down so many discovery pathways that i would never have found on my own !!!

A genetic marker to inform my response to Leflunomide is too late for me. I have already tried and failed Leflunomide. However, Prednisone probably contributed to the failure. Leflunomide was discontinued due to infections. My rheumatologist said Prednisone and Leflunomide together caused too much immunosuppression. Otherwise, Leflunomide was working.

I have had pharmacogenomics testing, at Mayo actually. Afterward, there’s a consultation with one of the pharmacists to explain it.

It was pretty complex, and I don’t exactly have a science brain, but it was my understanding that while the science is evolving, there’s still many limitations around what they can recommend based on the data they currently have. If I remember correctly, most of the existing data is based on genes that affect how your liver metabolizes medications.

But please don’t quote me on that because I’m not 100% on it, but the main idea was that because the majority of the research is focused on how one specific part of the body processes medications, it limits which medications they can advise on. And there’s also more data regarding some genes more than others.

The pharmacist specifically told me there isn’t supporting data for most of the kinds of medications used for autoimmune conditions. Drugs we discussed that I can recall were gabapentin, some antidepressants including amitryptaline, blood thinners, and there’s some cancer medications.

It was fascinating though and felt affirming because I learned I have a genetic variant that’s associated with metabolizing drugs more quickly, and the specific variant is involved in metabolizing around 30% of prescription drugs on the market. She said that might explain why I have trouble with so many medications.

What biologic did you end up with ?

I don’t have PMR; I’m actually a caregiver for my father who has PMR, so not sure if my experience is transferable.

But I’m on Humira; it’s a TNF blocker (a type of cytokine that causes inflammation). Before, I took Enbrel, also a TNF blocker. I have seronegative spondyloarthropathy (it affects the insertion points where tendon goes into bone, i.e. where the Achilles inserts into the base of the heel).

We had to do the usual trial and error approach. If pharmacogenomics were to advance enough, how great would it be to just be able to know which medications are must likely to work without having to go through potentially months to see which class and type of medications would work best?

Actemra (tocilizumab) got me off prednisone. There was a waiver granted because of my "inability" to taper off prednisone which was being used to treat PMR. Actemra was FDA approved for GCA at the time but not FDA approved for PMR. That was why a waiver was granted.

My rheumatologist thought Actemra "should work" for PMR but he didn't know if it would work or not. There were no promises made that it would work. I was just asked if I was "willing to try Actemra."

This happened 4 yours ago when IL-6 inhibitors were "looking promising" for PMR/GCA. I still do a monthly infusing of Actemra and it still works for me.

Humira ( TNF inhibitor) was also tried but it didn't work as well as Actemra did.

Thanks for that info, i didnt want to front up to my Doctor to request testing if there was no scientific basis for doing it. Just finding out if you are a slow or fast metaboliser is valuable when it comes to the drugs we are being asked to take. If you are a slow metaboliser, drugs are probably going to affect you for much longer and be more potent at lower than standard doses than if you are a fast metaboliser.