What the heck is PD-1 anyway? Immune therapy?

Probably the most talked about studies at the June 2013 ASCO in Chicago swirled around the newly released trials about PD-1 (Programmed Death-1) and similar.  “What the heck is this  all about, and why should I care?”, you may be asking.  This is important as it shifts attention back to the original immune therapies that kept me alive (and many others) when there was nothing else to offer any hope in the olden days of the 1990s.

Though a number of targeted therapies have since emerged, and  you have been hearing about them, there is new interest in the earlier and modestly successful immune therapies.  I  confess a fondness for anything described as an immune therapy, as I am alive–which I would NOT have been–without the first FDA approved agent against kidney cancer, high dose interleukin 2, brand name Proleukin.

The first new agents in the 2005+, the anti-angiogenesis drugs (not easy to pronounce,much less to understand) brought new hope to metastatic RCC patients.  With the late diagnoses of many kidney cancer patients, we desperately needed hope.  For about 14 years, HD Il2 (high dose interleukin 2) was the only game in town.  Nothing else existed,  so any patient lucky enough to hear about it, and not actively discouraged by the very “realistic” doctors, probably considered it.  This is a hospital-based agent which revs up the immune system, so the immune system would go after the metastatic disease, at least for some number of months or years.  That is why I am alive.  Nothing else was offered and nothing else was available.  Nine years!

Since that time the anti-angiogenesis drugs–translation: those that fight against (anti..) the creation (genesis) of angio (think blood vessels) drugs were approved. Think Sutent (sunitinib) and Avastin (bevacizumab) and others,. They have been the weapon of choice for oncologists and patients.  Why is that?  Though these drugs rarely offer more than some pushing back of the drug, decidedly welcome, they have rarely given more than some slowing or relief from the metastases, and always with some side effects.

For us old-timers, who faced only death, whether by efficient means or by surgical cut-and-pastes as holding actions, this was a tremendous breakthrough.  For these options, even if only holding actions versus mop-up operations, we were grateful.  We who had nothing previously were slightly scornful of those who complained about the side effects, as we were grateful to be around to have such effects.  The Stage IV sufferer  in 2004 knew too well that Stage V was a damn unpleasant journey and without a return ticket.

Now we have become greedy again, wanting more than the “stability” or “some shrinkage”, which I applaud.  We want success and life, not holding actions.  High dose interleukin 2 continues to offer that success to patients, but no one can predict which patients and  which conditions that might be likely.

Bless those researchers who continued to wonder why kidney cancer and melanoma (and maybe non-small cell lung cancer) respond to some sorts of immune therapies, and what happens to make that happen and not happen.  Those fine people have come to understand that the immune response which is revved up by HD IL2 has a complex set of “calls and responses” which either let loose the dogs of war/and immune responses, or fail to do so.

Most people understand that the body tries to protect itself from assaults, whether by poison ivy, bronchitis or cancer.  The immune system responds, gives the body aches, pains, fevers, chills, etc.  Think of flu and how rotten you can feel.  Think also of old diseases like Black Death which stimulated the immune system so violently that it was the strong and healthy with good immune systems that succumbed to the immune response, dying with lungs filled with immune reactions and fluids.  Only those with weakened systems and slower responses managed to live through the symptoms.

Obviously the body’s immune response needs a moderation, and not one that saves the village by killing it.  All of this leads to an explanation of the newest immune therapies, now in clinical trials in RCC.  You may hear about PD-1 and CTLA-1 trials, and how they may be helpful in kidney cancer, melanoma, and now in non-small cell lung cancer.

To understand all of this, it is helpful to think of a system of checks and balances, perhaps in an electrical or computer communication system.  Just as every electrical impulse might be appropriate, it could also do damage by overwhelming the system, burning it out, or failing to meet the requirements to be able to answer a “send me” signal.  So it is with the latest research on immune therapies with the PD or Programmed Death agents.

Keep in mind that the immune response is typically used against infections, and not generally against cancer.  I assume that we cavemen needed more protection evolution-wise against infections and less so against the ravages of cancer, which seems to result from getting older and getting overwhelmed by changes/mutations in the body.  (Not always, I know, but that is a discussion for later.)

T cells are supposed to react to a number of infections and such, and trigger an immune response to fight back against the “aliens”, such as cancer and ragweed. Just right amount of fight, and the body recovers.  Too little, and you have the devastation of the Black Death, an over-the-top immune response.

The  immune system is supposed to respond to handle the natural threats to the body, but not over react and set the system on fire metaphorically.   It had built in checks in balances, as do normal cells.  We see this everyday when our normal growing hair cells decide to stop growing and the hair fall out.  Chemo patients struggle with the balance of killing all cells, with the faster-growing cancer cells being killed off first.

New agents have been developed that interfere with a signaling system that puts the T cells, the protective/fighter cells into action against cancer cell.  This naturally happens, but the nasty cancer cells try to evade that process by interfering with that process.  Not letting the body protect itself, by disguising itself as the evil twin, equally eager to live, as the good twin, the healthy cell, cancer interferes with Programmed Death.  More next time…

And as Mae West said, “I like a man who takes his time.”…