You can read about IL-2 side effects in any clinical trial summary. They’ll list rigors, fever, hypotension, organ toxicity. Neat bullet points. Clean language.
None of it prepares you for what it actually feels like.
I received four doses of high-dose IL-2 as part of a first-in-human TCR-T cell therapy trial at the National Institutes of Health. The protocol allowed up to five doses. Many patients who received even one ended up in the ICU. I took four — and the nurses started calling me “the four-dose guy.”
This isn’t a medical overview. This is what it felt like from the inside.
What IL-2 Is (In Plain English)
Interleukin-2 is a protein your immune system naturally produces. In high doses, it supercharges immune activity — which is exactly what you want when you’ve just been infused with billions of engineered T cells designed to hunt your cancer.
The problem is that supercharging the immune system feels like being hit by a truck. Repeatedly. On purpose.
In my trial, IL-2 was given after the T cell infusion to help the new cells expand and survive. There was no guarantee it worked — most of the evidence came from animal models — but the engineered cells themselves were grown in IL-2, so the rationale was there. If it gave me even a slight edge, I was taking it.
The First Dose: “Rigors”
They warned me about “rigors.” That word sounded like shivering to me. Maybe some teeth chattering. Something you ride out under a warm blanket.
What I experienced was closer to a fully conscious seizure.
It started about thirty minutes after the infusion. A faint shiver. Then, within seconds, it escalated into the most violent shaking of my life. My entire body locked and convulsed. My jaw clenched so hard I was sure I’d crack a tooth. My muscles seized in ways I didn’t know muscles could seize.
I curled into a fetal position — not because it helped, but because my body did it on its own, like some primal reflex trying to protect itself from something it couldn’t fight.
My wife was in the room. She usually can’t stand seeing me in pain — especially pain that looks like someone preparing to die. But she held a steady, almost stone-cold calm. Her eyes started to water, but the tears hadn’t fallen yet. She just held my hand while I shook.
I kept scanning the room, watching the nurses’ faces the way a nervous flyer watches the flight attendants during turbulence. They never lost composure. They moved like this was routine — like they’d seen it a thousand times.
Maybe they had. Or maybe they’d learned long ago that showing emotion doesn’t help anyone in a moment like that.
The whole time, one thought kept running through my head: What in the hell have I gotten myself into? This is only the beginning. What else is coming — and can I survive it?
The Bargain
After every dose of IL-2, I swore I wouldn’t do another.
And then, eight hours later, when the next cycle came, I talked myself back into it.
Screw it. I’m strong. I’ve been through worse.
I kept returning to the same cold logic: if this gave me even the slightest edge, why fight this hard only to shortchange myself at the last second? So I’d brace, breathe, and take it again.
That bargain — the swearing off, the talking back in — happened four times. Each time harder than the last. Oddly enough, however, the rigor happened only during the first infusion. The sledgehammer to the chest is what continued with the following doses.
The Fevers
The rigors were acute. The fevers were relentless.
They hit every night. They’d start building around midday and then climb steadily until I was sitting at 101 or 102 by evening. This went on for almost three weeks. At one point I sincerely questioned, “My immune system has been permanently modified. Is this going to be what I must endure forever?”
Everything aches with a fever like that. Nothing is comfortable. You can’t get warm or cool enough, and you can’t escape your own skin. The nurses were cautious — mostly Tylenol. There was uncertainty about how ibuprofen might affect outcomes, and I wasn’t interested in taking chances. If avoiding something — even hypothetically — protected efficacy, I’d take the discomfort.
I’d already made that bargain with the IL-2 itself.
To cope, I created my own story: the fevers were proof the new sniper T cells were doing their job. The way the immune system responds to a cold or the flu — only this cancer was one hell of a “flu.”
The Nightmare
One night is burned into my memory forever.
I was in a dream state but also barely conscious — something between sleep and waking. The room leaked into it: the blinking monitors, the distant hallway noise, the faint blue glow of the bed controls folding into the scene. Everything blended until I couldn’t tell what was real and what wasn’t – mixed with the physical discomfort of extreme body aches, sweating, chills and nausea.
Then the feeling hit: restrained. Paralyzed by something I couldn’t see or name. Part of me knew I was asleep, but I couldn’t prove it. I was shouting inside my own head to wake up, to move, to do anything — and my body wouldn’t respond. I was trapped in a straight jacket of my own making.
In the dream I was trapped in a loop. Same sequence, over and over. Dark. Cold. Pure terror. I sensed entities around me — threatening, watching — but they stayed just out of focus, like shadows with intent. I ran. I hid behind a berm, convinced I was finally out of sight.
And then it reset. Again. And again. What felt like a thousand times.
At some point a thought settled in with a terrible calm: I’m in hell. Or purgatory. Or some kind of time loop I’ll suffer in for eternity. And with that came a second thought, even worse: This is my existence now. I have to accept it.
I kept pushing against it anyway — pushing and pushing — until, finally, I caught a glimpse of the outside world. With my body half-paralyzed and drenched in sweat, I forced myself awake.
The rest of that night I lay there with the fever still raging, aching all over, my head pounding. I was too afraid to drift back to sleep, even for a moment.
Why I Kept Going
People ask why I didn’t stop after the first dose. Or the second.
The honest answer: because I’d already given up too much to leave anything on the table.
I’d found this trial when three research teams had missed it. I’d let my tumors grow back just to qualify. I’d driven to NIH terrified, checked into a room I’d live in for a month, and let them wipe my immune system clean.
After all of that, stopping short of what my body could handle felt like quitting in the last mile of a marathon. Not because I’m brave — because I’m stubborn. And because the math from the very beginning of all this was simple: even a hypothetical edge was worth the suffering if it meant a better shot at being here for my family.
My doctors pulled me at four. They worried about fluid buildup in my lungs. They were probably right. One nurse told me about a patient who got the full five doses — he was so delirious he believed there was danger in the hallway and held her and his wife “captive,” armed with nothing but a box of tissues. He still landed in intensive care.
The Aftermath
A couple of days after my last dose, my trial doctor stopped in and was astonished to find me sitting by the window. Apparently that wasn’t normal for someone who’d just taken four rounds of IL-2.
The nurses kept stopping by. “Congrats. You’re a rockstar.” In a setting where victories are hard-won and often invisible, that acknowledgment mattered more than they probably knew.
Later came the scans and I knew all that fight and discomfort was made tangible for the first time. First: 18% tumor reduction. Then 41%.
The IL-2 didn’t do that alone. The engineered T cells did the heavy lifting. But IL-2 may have helped them survive and multiply — and I’ll never regret giving them every advantage I could. At the conclusion of that stage of the trial I thought to myself, “I don’t care what happens. I’ll never do that again”. But if you asked me the same question today, should a second infusion be necessary – I’d be on the plane tomorrow.
What I’d Tell Someone Facing IL-2
- “Rigors” is a medical euphemism. Prepare for something closer to a conscious seizure. It’s temporary, but it’s violent. In the grand scheme of things, it’s just a blip on the radar – even though it doesn’t feel like it in the moment.
- The fevers are the long game. The rigors are acute. The weeks of nightly fevers are what wear you down, and they will slowly resolve. You’re not doomed to a life of fevers and chills.
- Your mind will try to quit. After every dose, you’ll swear you’re done. That’s normal. Give yourself permission to decide fresh each time. It’s amazing what difference an eight hour break can bring. But, saying yes again, it’s a difficult decision no matter what you tell yourself.
- Watch the staff, not the monitors. They are the foundation. They are experts. Use their calmness to reassure yourself. They’ve been through it countless times – this is your first and only.
- Create a story that serves you. Mine was that the fevers meant the T cells were working. Maybe it was true. Maybe it wasn’t. It got me through the night.
- You are not weak for struggling. Most patients ICU after one dose. If you make it through even one, you’ve done something hard. You are one step closer, this has been a long journey. Hang tight.
I’m a stage 4 colorectal cancer survivor who received the first-ever TCR-T cell therapy targeting the TP53 Y220C mutation in a solid tumor, at the National Institutes of Health. I write about what treatment actually feels like — not what the pamphlet says. Read more about my trial experience: TCR-T Immunotherapy: What It’s Like to Be the First Patient
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