Updated Dosing for Keytruda...Someday

Immunotherapies continue to dominate the cancer landscape and are still the focal point of melanoma research. Cancer researchers release trial results at major oncology conference spread throughout the year in April (AACR), June (ASCO), and September/October (ESMO).  Usually, there are multiple sessions and announcements of progress towards treatment approvals. With the first conference, AACR, choosing to go virtual for 2020, the news was a little slower and more difficult to find.

Keytruda dosing updates for melanoma patients

There was one bit of good news for those who dislike going to the infusion center; your future trips may be cut in half. At the virtual meeting, the IMspire150 study team presented findings showing that one treatment of pembrolizumab (Keytruda) given at 400mg every six weeks had the same response as other dosing schedules, including the currently approved 200mg every three weeks.¹ In other words – a double shot of anti-PD-1 given in double the time gave the same results.

The researchers were trying to show there was little or no change in the efficacy (how well the drug works) with the new dosing regimen. Given that pembrolizumab's half-life – the time the concentration of the drug in your body is reduced by 50% - is nearly four weeks, it makes sense that the drug would have lingering effects, even as you prepare for your next dose.^2,3

Every 3 weeks to every 6 weeks

For example, the anti-PD-1 drugs are currently administered every three weeks. That means at week 12, there is still about 12% of the original drug in your body – not even counting the doses you would get in week 3, week 6, and week 9. Since the percentage of drug halves every four weeks, each treatment is building upon a pretty good framework.  At week 6, you're still cruising along with 38% of the drug still roaming around; if it were a baseball player, he'd be a Hall of Famer with that average.

The U.S. is lagging behind

The only issue with transitioning to this schedule? If you live in America, you can't yet get it. The US FDA rejected Merck's updating dosing application.⁴ If you live in the States and battling melanoma, you're not pushing back your anti-PD-1 infusions to every six weeks; at least not yet. The European Medicines Agency (EMA – the EU's FDA) has already approved the alternate dosing, so it is just a matter of time before the FDA follows suit.

And what is the nivolumab (Opdivo) schedule?

Meanwhile, nivolumab (Opdivo) is approved for both two and four-week schedules, which makes this even more confusing. You can understand a patient's confusion when they are told they could take nivolumab every 2 weeks, pembrolizumab every 3 weeks, Opdivo every 4 weeks, or Keytruda every 6 weeks...and they all mean basically the same thing.

Research is advancing, cost stays the same

Medicines get refined as research evolves. Pembrolizumab and nivolumab both broke into the cancer scene SO rapidly that the optimal dosing took a backseat to getting these drugs approved for as many patients as possible, as quickly as possible. A less-intrusive dosing schedule is a small but significant step towards getting patients the best experience possible. Unfortunately, the COST for the drug is unlikely to change, but it does mean half the visits, half the disruptions, half the aggravations, (hopefully) half the side effects, and half the reminders you are a cancer patient. When it ultimately gets approved, that is.