My reflections after following the REGAL / GPS debate closely (not certainty, but the distilled essence)

I want to be very clear up front: This is not a claim of certainty, insider knowledge, or “guaranteed success.” What follows is my best synthesis after reading a lot of debates, analyses, bear cases, bull cases, KOL comments, historical data, and trial design discussions around REGAL and GPS. Think of this as the essence of what can reasonably be inferred without seeing unblinded data. I may still be wrong — but I think this is close to the truth. What weakens the bear case (in my view) 1) “BAT is just living much longer now” is asserted more than demonstrated — especially in CR2 A large part of the bear thesis rests on the idea that modern BAT (often implicitly V+A) has dramatically improved OS in AML CR2 and can fully explain the event slowdown. The issue is population mismatch: • CR2 ≠ CR1 / upfront AML • Resistance biology, cumulative toxicity, infections, and marrow failure dominate CR2 outcomes • Data showing 15–20+ month median OS in CR2 BAT (without transplant) is very hard to find That doesn’t mean BAT hasn’t improved — but it does weaken the claim that BAT alone plausibly explains all of the observed timing. 2) Venetoclax + azacitidine is not a proven OS “game-changer” in CR2 V+A clearly changed the frontline landscape. But in CR2: • durability is limited • resistance is common • myelosuppression becomes dose-limiting • long tails are uncommon A lot of bearish arguments implicitly import CR1 results into CR2. That transfer is not biologically clean. 3) Open-label + real-world BAT cuts both ways Yes, open-label trials introduce noise. But in REGAL: • BAT reflects real-world salvage reality • toxicity and discontinuation are real constraints • if GPS is genuinely low-tox and maintenance-friendly, time itself becomes a differentiator Open-label doesn’t automatically favor the control arm. In an immunotherapy/maintenance setting, it can actually enable tail separation. 4) Event slowdown is not meaningless just because both arms could be improving The bear response is often: “Both arms are living longer.” That is possible. But: • degree and persistence of slowdown matter • sustained deviation from expected event cadence is statistically more compatible with a tail effect than with uniform uplift This is not proof — but it weakens the idea that timing contains zero information. What strengthens the bull case (again, not proof) 1) REGAL is arguably the best possible setting for a vaccine-like therapy Cancer vaccines fail most often when: • tumor burden is high • immune exhaustion is severe • disease is rapidly progressive REGAL is: • minimal disease • maintenance setting • post-response biology If a WT1-targeted immune strategy has any chance, this is close to the optimal context. 2) GPS ≠ older WT1 vaccines in a simple apples-to-apples sense The OCV-501 comparisons are understandable but incomplete: • monovalent vs multivalent • native vs heteroclitic peptides • limited vs broad HLA coverage That does not guarantee success — but it weakens the claim that “WT1 already failed, therefore GPS must fail.” 3) Phase 2 data should not be dismissed — but also not over-believed Yes, Phase 2 often overestimates effect size. That’s real. But Phase 2 still matters as a prior, especially when: • population matches Phase 3 • mechanism is consistent • signal is large rather than marginal The rational position is not “Phase 2 proves it” nor “Phase 2 means nothing” — but something in between. 4) The observed timing pattern fits known immunotherapy behavior Immunotherapies often show: • delayed separation • long-tail survival • benefit driven by durability rather than early response rates If REGAL is showing delayed event accumulation, that pattern is mechanistically compatible with immune maintenance. Again: compatible ≠ proven. 5) BAT biology in CR2 makes long survival tails intrinsically difficult Regardless of debate tone, CR2 AML remains: • biologically aggressive • clinically fragile • constrained by toxicity If a meaningful tail exists, it is more parsimoniously explained by a low-tox maintenance effect than by widespread BAT miracles. Where bulls still need to be honest • HR thresholds are unforgiving A trend is not enough. HR must clear the predefined bar. • Phase 2 → Phase 3 regression is common Even real effects often shrink. • Open-label variability can blur separation Noise cuts both ways. My bottom-line synthesis After absorbing a wide range of arguments, I think: • The bear case is weaker than it often sounds when scrutinized at the CR2-specific level. • The bull case is stronger than a simple “coin flip,” but far from guaranteed. • REGAL looks like a genuinely asymmetric setup: limited downside relative to potential upside if durability emerges. I am not claiming certainty. But if forced to choose which side is making fewer assumptions, the bull case currently requires less narrative stretch than the idea that BAT alone explains everything we’re seeing. That’s the essence I can reasonably extract — without pretending to know the answer before the data. Looking forward to hearing your perspectives?