RE: Cohort 518 Jan 2023 19:36
This is a good question, what will the next dose be? So far, it's been in 40 mg/m2 steps (80, 120, 160 and 200 mg/m2), so it stands to reason that the next will be 240 mg/m2. That's all well and good, except that the predicted MTD, based on the mice models is something like 4x the standard dose (the ava6k dose was 6x higher than the dox dose in mice, but one needs to correct for the weight difference (0.67), which brings it down to 4x). C1 was dosed at the equivalent of 54 mg/m2 (which was 90% of the standard dose, which would be 60 mg/m2). 4x 60 mg/m2 = 240 mg/m2 of dox or ~360 mg/m2 of ava6k.
So if we would keep going in 40 mg/m2 steps, it would take another 4 cohorts to reach this level. Also, as noted by Alan last April, systemic levels of FAPalpha are much lower in humans than in mice. So the MTD ratio (ava6k to dox) may much be much higher in humans than in mice. In this case, MTD would never be realistically reached in a P1a trial (i.e., you may need >10-20 cohorots).
It will be interesting to see if they keep going in 40 mg/m2 steps (which, given the above, is unlikely to reach an MTD), or if they kick it up a notch and start going in 60 or 80 mg/m2 steps.
Like others have said today, I expect an RNS in the next few sessions stating the next dosing level. Will be interesting to see, and may give the game away regarding the level of ava6k tolerated by humans. If they kick up the dosing level, this will be an extremely bullish sign. If they stick to another 40 mg/m2 increase, it may reflect that they expect MTD to be close, or may just reflect the conservativeness of the committee.