Hi, all. I've been on Besremi for two years now and wanted to share an update and my experience. It's been a very good experience, so far; and I'm optimistic that Besremi is both controlling my blood counts and modifying disease progression.
I'm 62 now. I was diagnosed with PV at age 44 and did nothing but phlebotomies until age 60. My hematologist/oncologist at a highly regarded cancer center (but not an MPN specialist) always told me I'd go on HU at age 60. I wasn't too worried about it; because it always seemed far away, and I felt fine on phlebotomies (just some fatigue).
At age 60, we moved to the Midwest; and I sought out on MPN specialist. He did a BMB, which showed disease progression (level 2 fibrosity), an allele burden of 88%, and 2 out of 10 abnormal karyotypes. (I'm not sure what the karyotype thing means, actually.) Based on an assessment of symptoms and the BMB results, the doctor determined I still had PV and hadn't yet moved to MF. He said, "We need to get you on an interferon." It was a battle to get insurance approval, but I started Besremi in June 2022, at age 60.
Besremi Dosing
He started me at 100, and we moved up by 50 every two weeks (with a couple exceptions). By mid-October 2022, I was at 500. I tolerated it well. I had some very slight nausea early on and some rashes/dry skin patches. I did experience some melancholy and mood stuff (not depression), but that subsided over time.
The drug brought down the platelets and WBC pretty quickly, getting to normal in about 4 months. It took longer to get and keep the HCT in the normal range -- about 11 months.
About 15 months after starting the drug (September 2023), some of my counts were getting too low (platelets under 100, WBC below normal); so we started backing off the drug. I'm now at 250 and will probably stabilize at that level.
I know this dosing was more aggressive than some doctors think appropriate, but I was game for it as long I was tolerating it. I was all about going after that allele burden and hoped the high dose would help with that.
Progress
In June 2023 (after being on the drug for a year), we did another BMB. The two abnormal karyotypes had disappeared. The fibrosity hadn't gotten worse. The allele burden had gone down to 80% - still super high, but better.
In May 2024, the doctor checked the allele burden through blood work. It was 35.4%! I didn't believe this, so I waited to share it until after my Dr. visit last week. It is true! Hey, it's higher than a lot of other people; but a lot lower than where I started.
Symptoms
Two other things have happened since being on Besremi. The terribly annoying itching after showers has gone away completely, and I'm no longer waking up at night throwing off the covers because of heat. My spouse and I no longer argue about how cold we can get the bedroom. 
I'm not sure what led to this, but maybe the lower allele burden?
When talking this over with my Dr., he said the interferon is "toxic" to the JAK2. It can take a while, but it eventually "breaks it." He also said that data shows that the interferon does most of its work to reduce the allele burden in the first three years, stabilizing after that.
So, I'm very thankful to be on this drug, hoping it keeps working, and hoping all of you have the best journey possible as we deal with these MPNs.
Also, especially if you were diagnosed at a young age, talk to your doctor about treatment, other than phlebotomies. Don't assume that because you feel good and tolerate the phlebotomies that nothing is going on inside that bone marrow. These cells are sneaky. They're reproducing, even if we don't feel it. My only regret is not getting on Pegasus as soon as it was a treatment for PV.
Besremi -Six Week Update 
Ramblings on Pre-PMF and early stage MF
Longterm Interferon treatment
