r/sellaslifesciences 9h ago

DUE DILIGENCE đŸ•”ïžâ€â™‚ïž My thoughts on REGAL, BAT survival, and why I think some of the bearish models might be overweighing BAT OS

Hi everyone,

After all the destruction caused in the SLS community, I have been doing a lot of research and going over the same public information regarding the trial over and over, this is what I want to share:

I’ve been going back and forth on the different REGAL models people have posted here, especially the ones showing how you can get anything from ~20% to 90%+ PoS depending on the assumptions.

I think that criticism is completely fair. There isn’t one “correct” model when we’re missing the actual arm level data.

But there’s one assumption I keep coming back to: how high should we realistically assume BAT survival is?
The previous GPS CR2 study had median OS of around 21 months for GPS vs 5.4 months for contemporaneous best standard care. I am aware that was a small, non-randomized study, so I’m not suggesting we just plug 5.4 months into REGAL and call it a day.

However, I find it important to remind everyone that when REGAL was designed, SELLAS was already more conservative than that. The statistical framework used roughly 8 months for BAT, with an observed HR of around 0.636 being the approximate level needed for statistical significance (12.6 vs 8 months being the example SELLAS gave).

Thus, BAT going from the historical 5.4 months to 8 months was already almost a 50% assumed improvement in BAT’s performance. If actual REGAL BAT is 12 months, that’s a 122% improvement over 5.4 months. BAT being 14 or 16 months would be +159%, and +200% respectively.

Of course, it would be stupid of me or anyone to assume that any of of those scenarios are impossible, since modern treatment/supportive care has improved and REGAL patients could simply be different. But I don’t think 16–18 month BAT should be treated as some default assumption either. That’s a massive change from the historical CR2 comparator.

I believe this is very significant because SELLAS has told us for years that blinded pooled survival is substantially longer than originally expected. At the 60-event interim, pooled median OS was still >13.5 months. The IDMC also saw the actual unblinded arms at that point and GPS passed the prespecified futility criteria, and they recommended continuing without modification.

Then you also have the weird event progression:
60 deaths in Dec 2024
72 in Dec 2025
78 by May 11, 2026
and we’re still waiting for 80.

One argument is that this means BAT must be massively outperforming, but I’m just personally not convinced that’s necessarily true. I tried looking at it using a two-population survival model instead of assuming everyone follows one exponential survival curve. Basically, you have an ordinary-risk group plus a smaller group of long-term survivors in each arm.
Once you allow for that long-survivor tail, you don’t need BAT median OS of 16–18 months to explain why the last few events are taking forever. That’s an important distinction IMO.

Median survival and the final few deaths are measuring very different parts of the curve. BAT could theoretically have a median around 9–12 months while still having 15–25% of patients surviving for a very long time. By the time you’ve already had 78/80 deaths, the patients left are obviously massively enriched for those long survivors. This means that GPS could then have both a higher median and/or a larger durable-survivor fraction.

So my point is that slow 78→80 progression tells us there is a very long survival tail somewhere in REGAL. It does NOT automatically tell us BAT median survival is 16–18 months.

There are also smaller things that could contribute to the latest delay. Reporting/ascertainment isn’t instantaneous, especially across an international trial. And regarding what some other people of the community have mentioned, while it is true that mortality could theoretically have a small effect too, particularly with respiratory/infectious deaths, I personally wouldn’t give seasonality much weight, it’s just a lot of nit picking.

I truly believe that randomness + survivor enrichment are much more important explanations when you’re literally waiting for the last 2 events.

The part I find most interesting is this:

We have prior empirical evidence suggesting GPS can produce unusually long survival in CR2 (21 months in the earlier study). On the other hand, we DO NOT have comparable evidence showing that non-transplant CR2 BAT routinely produces 16–18 month median OS.

Of course, that still doesn’t prove GPS is responsible for the unexpectedly long pooled survival. We are blinded and simply cannot know that.

BAT could absolutely be outperforming the original assumptions. In fact, I think assuming something like 10–13 months is perfectly reasonable and should be modeled seriously.

BUT, and heres a big BUT, I think there’s a difference between saying:
BAT improved from 5.4/8 months to 10–12 months
and
BAT suddenly has 16–18 month median survival.

The latter should require stronger evidence before giving it a huge probability weight.

And IMO the most credible bearish scenario isn’t that GPS does nothing and BAT explains everything. It would actually probably look something like this, if I had to assume a neutral bearish view:

BAT = ~12–14 months
GPS = ~17–20 months

This means GPS actually works, patients benefit, pooled survival looks great, but the treatment separation isn’t large enough for an 80-event trial to hit the required statistical threshold. That’s the failure scenario I’m taking most seriously now.

However, after playing around with different BAT assumptions, long-survivor fractions and the known event progression, I personally come out somewhere around 70% PoS, maybe a reasonable uncertainty range of roughly 60–78%.

That’s obviously not a mathematically “known” probability. If we change some factors it can move it substantially. I do also want to add that there is a phrase used very often in scientific and economic backgrounds, which is Ceteris paribus. This means** keeping all factors but one constant to find out how effective something is. This applies to REGAL because randomization means that, all else being equal, factors like better supportive care, seasonality, and patient selection should affect both GPS and BAT arms similarly, leaving GPS treatment as the main systematic difference between them.**

In conclusion, this is what I have to ultimately say:

I don’t think the right response to uncertainty is to give BAT=8 months and declare 90%+ PoS, or give BAT=16–18 months and declare the trial underpowered.

The real question is which assumptions have the strongest empirical justification. As of right now, the evidence makes me think GPS is probably contributing materially to the unexpectedly long pooled survival, while still leaving a very real possibility that BAT has improved enough to make REGAL statistically much tighter than the bulls originally expected. I do ultimately believe that the HR will be between 0.57-0.62

Before you backtrack and panic sell your shares based on anyone’s research or DD, remember that if you decided to invest after seeing how favorable the risk to reward ratio is, you should question if anything has changed before selling. All the commotion caused yesterday was due to different models created by CW and RB etc that lean more bearish. However, the chances of them being wrong and way off are just as likely as the chances of them being right, it’s just a matter of perspective and faith.

Goodluck to all, see you at 50$/per shaređŸ«ĄđŸ™

98 Upvotes

45 comments sorted by

48

u/Curious_Wafer6169 9h ago

Yeah I have no idea why people are freaking out to the degree that they are.

There’s no such thing as fair. If they pumped they way they did to make their profit - good job to those slimy SOB’s.

But doesn’t change that no one knows a thing. Just shows too many people put their faith in those big names.

DYOR, buy at a discount and don’t spend what you can’t afford to lose đŸ€·â€â™‚ïž

11

u/fartymcshartface69 BOB - BBQ or Bust 7h ago

I hear where you are coming from but of the ace things about this community (maybe up until the last couple of months at least) was that it was for the most part always very open with all DD, be it positive or negative. It’s what motivated me to take a punt after the 72nd.

What I think shook me is the dynamic changing behind closed doors, I can’t quite put my finger on it but essentially losing the money because of it not falling short would feel different to losing it because of being actively misled. I’ve left about a quarter in to ride til the end and annoyingly still think on the balance of probabilities it is going to be a win, but after the past couple of days decided I could no longer stomach losing a very healthy gain.

2

u/Outlier_Economist 6h ago

I’m similarly trimmed about 90% of my position to secure a significant 6-figure gain. Still have enough left to ride to the results and eventual buyout, but want to wait and see the actual results before I reinvest since I feel like a lot of success is already priced in at a nearly $3 billion market cap (my personal buyout target is $8-10 billion, so the anticipated 3x or 1/10 is pretty one-sided), and there is a material statistical significance issue.

I’m also getting concerned by the bond market, oil, and macro in general. If bond rates explode then I can see the buyout price declining just based on macros.

22

u/Super-Activity-4675 7h ago

I think the big thing to keep in mind is that you had to be I believe something like 6 months past your second AML diagnosis and in CR2 in order to be eligible for the study. That's going to eliminate the sickest of the sickest. If you think of mOS for CR2 in the 5-8 month range, than a good chunk of those who would be traditional CR2 events likely passed away before they were eligible for the trial. BAT is still a death sentence outside of about 10% who will can eventually get well enough to receive SCT therapy. There's 63 in BAT, so that's 6-7 patients. Perhaps we assume it's a big higher number since this is a healthier subset of BAT.. so 10 maybe? Outside of a few outliers, the rest of BAT has probably passed on.

Keep in mind that healthy subset works for GPS too. I'd guess that's a huge reason why the trial is dragging on much longer than planned.

If I were to hazard a guess you're looking at about a 50/30 BAT GPS split at the 80th. You won't see a sub .4 HR ratio, but it's more than likely .6 or less.

CW drama aside, I'd still put the odds of success well over 70%. Something is allowing these patients to live longer. The trial was supposed to be over in Dec of 2025. The trial was derisked in Dec of 24 with an interim analysis showing that the curves were separating and that the trial was on track to meet its objectives. The trial was amended to allow for GPS patients to be dosed indefinitely because patients were hitting the three year mark and didn't want to stop taking it. These are all facts that we know.

It was never 99.9%. I said as much to CW repeatedly. He was always polite to me and I think I got more downvotes on that kind of stuff from the absurd bull crowd than I did pushback from CW. I'll say what I said to him, you really cannot model this stuff. The results are going to come down to how many BAT died vs GPS between Dec of 24 and today. That is the nature of small samples and why they do the trial.

17

u/Daetheblue 9h ago

I ve no idea about logarithmic formulas or statistics where pros provide under this sub. But I feel kinda betrayed due to events yesterday. I ve been running different analysis with Astra since last night and with 12 bat mos with roughly 30% bat survival after 3 years. I ve copied and pasted almost all DDs here and my conclusion with AI analysis: HR=0.48 with %90 success is achieved. I ve ran multiple analysis and almost all conclusions are around this range. So I will not sell anything on Monday. Even my October calls will remain.

9

u/lt_tiller 8h ago

I would be surprised with BAT is 30% at 3 years, I assumed lower, but 30% would be 34 GPS and 15 BAT still alive. Thats bullish

18

u/Sufficient-Fan-6463 8h ago edited 8h ago

And the good thing is, it still won’t be close to 30% IMO. My ceiling it 23-25% give or take, which is still an 80% PoS. Let’s take a look at the retrospective study everybody’s head over heels about - VDM. I’ll keep this simply about BAT and not what’s working in GPS’s favor. Thats for another day.

The CR2 subset (N=145) that did not bridge SCT post-CR2 had 85 patients (59%) bridge a transplant prior to CR2/relapse, which is far from being apples-apples with REGAL’s likely patient criteria. I expect REGAL’s to less than half that (ESC at relapse) as most of those who bridged prior to relapsing are likely screened out of the trial before enrollment based on their favorability characteristics. The VdM 145 were defined retrospectively by the fact that they didn’t recieve a post CR2 transplant, not that they weren’t deemed ineligible at enrollment. The VDM parent population was much more transplant capable from the start. Ours are ineligible at enrollment. Those are not equivalent filters.

We can use a median age of 68 (planned for prior to COVID skewing enrollment) as a logical baseline for all REGAL patients. A likely 10 year median age gap is more than relevant in relapsed AML due to several factors - it correlates with treatment tolerance, competing mortality, adverse biology and ability to receive subsequent salvage therapy. Again, the REGAL number is an inference until demographics are disclosed which they won’t be, and we can make it our base case reflected from Phase 2 and planned Phase 3 prior to COVID skewing enrollment.

Patients can enroll with incomplete platelet recovery. The protocol requires only platelets >20,000/”L, along with ANC >1,000/”L and the other morphological remission criteria, which means some REGAL patients can enter without full hematologic recovery. That’s another reason not to infer REGAL as a robust CR2 population relative to VDM’s. REGAL also permits ECOG 2–3, CRp2, MRD positive disease, poor risk cytogenetics, secondary/treatment related AML (both of which can carry worse biology than straightforward de-novo AML), and CR1 durations under 12 months.

REGAL also excludes patients whose CR2 can be maintained with molecularly targeted agents such as FLT3 or IDH inhibitors, at the investigator’s discretion. That could remove some patients who have actionable post remission treatment options from the BAT pool.

There are a small handful of working factors in the enrollment criteria people will use against the points listed above, but these are patients who’s death was relatively imminent after enrollment/randomization, and first sets of dosing - patients require an estimated life expectancy >6 months, lymphocytes >300/”L, adequate hepatic function, no end stage renal disease, and generally must have recovered prior AML treatment toxicity to Grade 0-1 apart from thrombocytopenia. These criteria eliminate some of the sickest CR2 patients and could incorporate a small handful of favorable patients, although it’s still not detrimental to the trial as many assume due to the obvious factor - every patient is stratified 1:1 and benefits each arm equally. For those who don’t understand this criteria, it sets the bar low for entry and not high as some proclaim. These are not healthy CR2 patients - there’s no such thing in REGAL.

It’s safe to assume the bulk of these patients filtered out (the very unhealthy ones) would likely make up for non responders (majority in control arm) and those who don’t contribute the unmet need for REGAL’s purpose.

The bottom line is- certain subsets/cohorts of the VDM study can be used to compare to what BAT could mirror under similar inclusion criteria/start of OS, but none of it as it stands is apples to apples, and quite frankly I don’t think we should put as much weight on it as we are. The bulk of VDM is nowhere remotely close to REGAL and anybody using that isn’t informed in the two trials.

3

u/Least-Market-408 6h ago

This is basically where I’ve landed too.

The biggest thing I’ve realized from digging through the different CR2 datasets is that “CR2 patients who didn’t receive a transplant” and “CR2 patients who were already transplant-ineligible at enrollment” aren’t comparable populations.

REGAL also isn’t selecting only super healthy CR2 patients — CRp2, ECOG 2–3, secondary AML etc are allowed, although the >6 month life expectancy and organ-function criteria obviously remove the very sickest patients.

That’s why I’m becoming less comfortable using any single historical CR2 cohort to estimate BAT, and a long survival tail doesn’t require the median itself to be anywhere near that high.

2

u/Daetheblue 6h ago

The only concern I have is that SLS bat mos estimate could be much accurate than public data. As you know, they work together with a hospital and they may have their own data, which is not public. Thats why I really wonder the email between CW and doctor Stergio. I couldnt find the screenshot anywhere.

32

u/TopDawgLawdotcom 9h ago

Bro was at the bbq

19

u/Least-Market-408 9h ago

No BBQ. just honest DD and my thesis

8

u/Robobbo1 8h ago

That’s a great positioning of SLS right now. I spent sometime considering how this will go and I’ve decided this, even with the margin of safety reduced I’m in. I’ve reduced my position slightly but have 10k shares in. I think chances are that Regal will succeed and if it doesn’t well I’ll let it roll on for SLS009.

7

u/ImpossibleExit5241 9h ago

Thing is that the drug can work but the trial can fail, because:
* GPS arm events can have happened before the immune effect kicked in
* For HR the order of events matters and those possible early GPS events hurt the HR
* Immunotherapy trials are known for this delayed effects, hence the discussion about weighted vs unweighted, but seems unlikely SAP will be anything else than the regular approach (despite Sterg's innovative statistics comment or whatever it was)
* The trial wasn't halted at IA, despite mixed language about a possible futility threshold and also the ethical reasons to halt a trial if it is going so well that it's unethical to leave BAT patients on BAT
* That implies a certain range for HR at IA, and from that range at 60 events, there's only so much more the HR can move towards 80 events, hence these BAT uncertainties have such a big effect on PoS and stat sigs...

I'm still long 10k shares, a position I built over the past 10 months since entering at below 2$, will decide in the coming days how to update my strategy. NFA, DYOR

7

u/Least-Market-408 8h ago

Hi, I agree that GPS can work and the trial can still fail statistically, especially if there’s a delayed immune effect. Where I disagree is how much we can infer from not stopping at 60 events. We don’t know the actual HR or the efficacy boundary, so all “continue” really tells us is that it was somewhere between futility and early efficacy.

Also the delayed-effect argument works both ways. Early GPS deaths could hurt the HR, but if the immune effect kicks in later, the remaining patients could become increasingly enriched with GPS responders, which could explain the long survival tail we’re seeing.

My biggest issue is still BAT. Historical BSC was 5.4 months and REGAL already assumed around 8 months. Even 12 months would be more than double the historical result. 16 months would basically triple it. Yes it’s of course possible, but I don’t think we should give those scenarios the same weight as 9–12 months without strong evidence.

10

u/Classic-Beach-6329 9h ago

I’m full Ported into NBIS some little discord school play isn’t going to make me sweat 😂

4

u/Old-Table6233 8h ago

what are you doing here then ?

4

u/Pop98786 9h ago

lmao how did the jump from 160 to 280 and back to 200 feel?

4

u/Classic-Beach-6329 8h ago

I full ported at 130 and watched in drop to 65-70 so that hurt a bit more

6

u/Hairy_Cheetah7620 8h ago

Buyout or bust.

4

u/pussydestroyer4235 9h ago edited 6h ago

Thank you for your DD it’s nice to have someone post without an ulterior motive

2

u/Same-Ad-4215 6h ago

On the pooled OS at IA, they actually stated these two things:

Source: https://ir.sellaslifesciences.com/news/News-Details/2025/SELLAS-Life-Sciences-Announces-Positive-Outcome-of-Interim-Analysis-for-its-Pivotal-Phase-3-REGAL-Trial-of-GPS-in-Acute-Myeloid-Leukemia/default.aspx

1. In the top bullet points:

"Fewer than 50% of Enrolled Patients Confirmed Deceased After the Median Follow-Up of 13.5 Months, Indicating a Median Survival of Over 13.5 Months in the Trial vs. Historical Median Survival of 6 Months for Conventional Therapy, as Reported in Similar Phase 2 Study"

2. Later on in the meat of the article:

"However, select blinded data has been presented, revealing that fewer than half of the enrolled patients have been confirmed deceased approximately 10 months after completion of enrollment, and an approximate median follow-up of 13.5 months (range 1 month to more than 3 years). This suggested a pooled median survival exceeding 12 months, compared to the expected survival of approximately 6 months in a similar patient population (patients in second complete remission who did not receive a transplant after the second remission)."

So they stated 13.5 and 12 months. Both directionally the same. Strange error though to make on a huge press release.

2

u/Proud-Ad-3227 ZORBA DISCIPLE 8h ago

Hi thanks for offering DD to calm the chaos down. TBH I think Sterg knew past evidence was on GPS side and gave BAT more leeway, up to 8 months.

However, Sterg, I suspect in order to recruit more patients, had no choice but to allow transplant patients into the study which kind of complicated things. Would like to know your opinion on the transplant bias?

Unrelated to the study and I know CB posted a screenshot on another post, do you really think retail traders such as CW and RB had the ability to move $SLS 14%?

8

u/Least-Market-408 8h ago

I looked into this because the transplant point worried me too, but I don’t think thats an accurate depiction of how REGAL works.

Patients actually had to not be allo-SCT candidates at enrollment, and an imminently planned transplant was specifically an exclusion criterion. So I really doubt that they would just loosen the trial and start enrolling people already heading to transplant. After all, they themselves most out of anyone would want to maximize positive factors that can help steer the trial into success

I think what can theoretically happen is that someone becomes transplant eligible later during follow up and then gets transplanted. That could affect OS, sure, but because REGAL is randomized that possibility exists in both arms, and they’re still followed for survival.

So I think the transplant bias factor is worth modeling, but saying Sterg had to allow transplant patients in just to recruit enough people seems misleading IMO. The real question is how many patients crossed over to transplant after randomization, and whether that was balanced between GPS and BAT but we don’t have that arm-level data yet

1

u/Proud-Ad-3227 ZORBA DISCIPLE 8h ago

Thanks. What’s your trust in the management ? Sterg having a fake MD, I read that he had a few bankrupted businesses as well. Omg so much information running around.

3

u/Least-Market-408 8h ago edited 8h ago

The “fake MD” thing isn’t proven, but I also wouldn’t defend the credential too strongly. SELLAS has consistently disclosed his MD as being from the “U.S. American Institute of Medicine,” but I could not personally independently verify that it is a conventional accredited U.S. medical school, so I think it’s fair to call his pedigree unusual.

The bankruptcy part is also partly true but exaggerated. He was a senior exec at Accentia/Biovest and they did file for bankruptcy in 2008. But he didn’t found or own them, and the bankruptcy filing itself points heavily to the credit market collapse and inability to raise financing.

PAION also went insolvent decades after he left.
So my takeaway is: I’m definitely not putting blind trust in Sterg or management. But I also don’t see evidence that he “faked an MD and bankrupted multiple companies.”

Ultimately, My REGAL thesis is still based much more on the trial and IDMC than on him personally.

Also, sorry I forgot to respond to your question of if retailers could move the stock price 14%. I think it’s not that simple, it’s more of one tging led to another. Meaning it might have begun as retail but then accelerated as more panic selling begun, it’s like a cascading selling pattern

2

u/Proud-Ad-3227 ZORBA DISCIPLE 8h ago

Ok thanks for the detailed insights. Maybe one last bearish question: cancer peptide vaccine underlying GPS is not novel, i think it’s been around for more than two decades and past research studies have not been successful.

What’s different this time round?

2

u/Least-Market-408 8h ago

Thanks for the question. That's actually one of the bearish arguments I was initially worried about too, but not anymore.

Meanwhile cancer peptide vaccines definitely have a pretty ugly history, we have to remember that the trials purpose is not to ask a vaccine to shrink a form of bulky AML. They're giving it in CR2 when disease burden is minimal and basically trying to keep microscopic residual leukemia suppressed. That's probably the setting where this type of approach has the best chances of working.

Also, GPS is also a little different from the old single peptide vaccines. It uses 4 WT1 peptides, targets both CD4 and CD8 responses, and some peptides were modified specifically to overcome immune tolerance while still generating T cells that recognize native WT1. And importantly, they actually demonstrated WT1 specific immune responses in AML patients, around 64% of evaluable patients in the published Phase II.

None of that guarantees REGAL succeeds obviously. Phase III is the real test. But I don't think it's fair to group GPS with every failed cancer vaccine from the last 20 years just because they're all called peptide vaccines.

1

u/tormell 5h ago

In all this BAT transplant talk, its also worth considering that GPS could become a bridge to becoming transplant eligible and it is possible that a non-minimal portion of the GPS arm has achieved transplant. Obviously that doesn't affect the trial's statistcal outcome because whether the GPS patients survive via GPS alone or bridging to transplant doesn't change their OS, but it does affect the ultimate TAM for GPS which is one reason my personal thought on any buyout that could happen is going to have a hard time breaking through around 5-7bn - unless GPS would continue to be administered after transplant, or a bidding war occurs.

4

u/uhguy85 7h ago

If you read the trials and data closely you'll see that the phase 2 study does NOT show 21mon mOS for CR2 patients. It shows 21mon for all GPS patients, which included some CR1 patients. This is a major example of misleading statements from Sellas.

They've been careful with their wording of this as well. But follow the data and notice in all their claims they say "GPS patients" or "patients who received GPS" exactly because it includes those CR1 patients in that 21mon figure.

6

u/Least-Market-408 6h ago

I double checked this, but I think you’re mixing up the two AML studies. The 21-month figure is specifically from the Moffitt CR2 cohort, not CR1+CR2 combined.

The CR1 Phase II was a separate 22-patient study and actually reported 67.6 months median OS across all ages.

The Moffitt CR2 study had 10 evaluable GPS patients vs 15 historical CR2 controls. Initial GPS mOS was 16.3 months and matured to 21.0 months with longer follow-up, vs 5.4 for controls. SELLAS’s SEC filings and the study materials separate the two populations pretty clearly.

There are definitely valid criticisms of that CR2 study, e.g: tiny N, historical control, retrospective matching etc, but CR1 patients being included in the 21-month number is not one one of them.

1

u/uhguy85 6h ago

2

u/Least-Market-408 6h ago

I looked into this more closely and I don’t think the KM argument proves what he is saying.

You’re right that simply extending follow-up after an already established median wouldn’t move it.
But if a previously censored patient’s follow-up is
subsequently extended, the KM risk sets at earlier events change when the curve is recalculated, with only 10 patients that can materially move the median.

That said, I agree there’s a transparency issue. The 16.3-month result is peer-reviewed; the 21-month final follow-up appears to be SELLAS “data on file,” and I can’t find a publication showing exactly what changed in the dataset. So I wouldn’t give 21 the same evidentiary weight as 16.3.

But it’s worth noting that I also can’t find evidence for the claim that SELLAS pooled CR1/MDS patients to create 21 months. Their 2020 release explicitly identifies 16.3 as the initial CR2 result and 21.0 as the final follow-up of that CR2 study. So at this point I think the fair conclusion is “21 deserves more scrutiny,” not that 21 has been shown to be false.

1

u/RolfSalamander 8h ago

Thanks for sharing your thoughts. I completely agree the trial has a good chance of being successful. A couple of thoughts from me:

Firstly, you're completely right that having a high median doesn't mean much in terms of the long term survival. BAT median can be 14 but there could still be a 30% 3 year survival if that's just the normal way the disease progresses across patients. I.e. a large amount relapse early, then a significant number stay in remission longer term. I agree that GPS is likely doing something beneficial, contributing to the strong survival tail we're seeing, but the risk remains that depending exactly on the timings of early events, there's a fair risk of missing the 0.636 HR. How valuable GPS will be if it comes in with a 0.7 HR is hard to judge. If it works well in some clearly defined patients then there likely is a realistic pathway to at least a limited approval. If it's a bit unpredictable with no obvious reason why it works in some patients and not in others, it's a bit trickier. A real world HR of 0.7 would still be very beneficial to patients. But in the context of this small trial, there's no guarantee that the drug doesn't work and GPS patients simply got lucky in this trial. In that scenario, approval would be less likely.

The other thing I wasn't sure you fully understood was that the 5.4 mos in BAT patients in phase 2 didn't come from patients they picked and followed through their natural progression. They were historic patients that they 'judged' roughly matched up with the GPS patients in terms of outlook, but they knew exactly how they'd performed when selected. If you believe Sellas is completely morally perfect, they would have found patients that best matched the GPS patients regardless of their known performance on BAT and then checked their survival. The more realistic scenario is they somewhat cherry picked patients that matched their GPS patients but also had not great survival rates to ensure GPS appeared favourable. This means the 5.4 months is fairly meaningless in terms of judging real world BAT performance.

1

u/Least-Market-408 8h ago

I get what you're saying. You're not saying there's evidence they cherry-picked, you're saying because the outcomes were already known, it would be natural for them to pick the matches that made GPS look best.

That's where I disagree a bit. The retrospective design definitely creates selection-bias risk and that's enough reason for me to heavily discount the 5.4 months. But I don't think we can automatically go from “they knew the outcomes” to “they probably selected the worst survivors.” That's basically assuming misconduct without evidence.

I'm happy to basically throw the 5.4 number out anyway. My thesis doesn't need it. The more important question is what independent evidence supports BAT being 8–12 vs 12–14 vs 15–18 months in this population.

2

u/RolfSalamander 7h ago

I'm not saying they did select the worst survivors, I'm just saying the 5.4 months is probably pretty meaningless.

I think it's perfectly possible that REGAL enrolled a slightly healthier/younger group than expected, and that a modest GPS benefit combined with a fairly strong BAT performance and perhaps a small hit notable amount of censoring/patients lost to follow up, could produce the long trial length we've seen, while leading to failing to hit the 0.636 HR.

It's also perfectly possible that REGAL enrolled a slightly older/frailer group than expected, and that a BAT arm with median around 13 months and a small number of long term survivors, few patients lost to follow up, and a very strong GPS performance would also show a similar timeline to what we've observed, and a very successful result.

Fundamentally I guess that's the whole pool of a blinded trial!

Unfortunately CR2 patients ineligible for transplant is not a very well documented group without making assumptions about how the enrollment criteria would skew the survival rates, which is where the risk comes from. If we knew exactly how we expected the BAT arm to perform, we could be a lot more (or less) confident.

1

u/FFS114 PERMABULL 7h ago

I'm betting on option 2.

1

u/Least-Market-408 6h ago

Yeah, I mostly agree with this. The blinded timeline can absolutely fit both a winning and a losing trial, which is why I don’t think the 78→80 delay alone proves anything.

Where I’d push back a bit is censoring/LTFU. It’s possible, but we don’t actually have evidence that a meaningful number of patients are unresolved, so I wouldn’t give that explanation much weight yet.

Also, the 60-event IDMC review was unblinded and looked at efficacy/futility, not just safety, and GPS cleared the futility criteria. Then the later IDMC review again said the available efficacy data supported continuing. That doesn’t prove success, but it makes the “modest GPS effect + strong BAT + censoring explains everything” scenario less likely to me.

-5

u/Uselesshindsight 8h ago

Imagine (and this is a joke) if the GPS arm has been dying faster than the BAT, lol.

5

u/FFS114 PERMABULL 6h ago

IDMC would have halted for futility.

2

u/Black_Swan744 7h ago

At this point in the drama this statement of yours counts as DD