dewophile
15 hours ago
Yeah, the Covid drug pivot really killed this company last couple years
covid itself hurt the RSV program - there was no RSV to speak of in the 2020-2021 season, and a very atypical spike much earlier seasonally than expected that was severe but very short in 2021-2022 that seemed to catch them off guard. So that cost the RSV program 2 years
As for the covid drug, after seeing ensitrelvir succeed in the prevention setting where paxlovid failed which could create a new regulatory path, and reviewing PFE's second gen data I think ENTA's program is mostly dead, but not completely dead.
PFE’s second gen sars cov 2 PI showed a virologic response, but did not show any resolution in symptoms in standard risk patients https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciae529/7863440?login=false, while EDP DID show a reduction in total symptom scores https://www.enanta.com/wp-content/uploads/2024/04/P0423_ECCMID_2024_SPRINT_Poster_FINAL.pdf
I know 235 is collecting dust, but hey it seems to have some oomph on symptoms that PFE's drug is lacking, and PFE is trying to run a PBO controlled phase 3 in high risk patients with hospitalization as an endpoint which seems awfully challenging to me with paxlovid available for those at high risk. The study listing has not been updated for a while now fwiw, so who knows if it started recruiting last week as planned https://clinicaltrials.gov/study/NCT06679140?term=PF-07817883&rank=8
The rub on 235 was virology, but if you compare the data closely PFE showed a virologic response but they also restricted enrollment to those with more than 4 log virus at baseline and ended up with 5 log baseline VL vs ENTA at 4 log. Remember enta did show a modest virologic response in those with 5 log or more at baseline.
dewophile
2 days ago
The market clearly thinks the RSV drug is going to fail. The bear case is basically that other drugs with positive challenge data failed when tested in real world scenarios, including Zeli in standard risk adults. The only one that nominally succeeded - ziresovir, Ark bio's fusion inhibitor - had a benefit in hospitalized peds patients but the clinical significance remains unclear. The company touts the benefits of a replication inhibitor, but lumicitabine a nuke polymerase inhibitor and replication inhibitor which was halted, failed to show a benefit in the enrolled patients before the halt. In adult patients GILD's fusion inhibitor failed in the transplant setting. The recent peds data, while definitely positive on virology, has some overhang on clinical endpoints. "Top notch" data would have shown a trend on some clinical endpoints other than the evolving resolve-p tool they are working to validate. So that is the backdrop.
The bull case as I see it, with a focus on adult HR patients now that that is the next big readout is as follows:
1. lumicitabine, the only other replication inhibitor with data AFAIK, failed in peds and adults, but in peds where there is published data showing a lack of virologic benefit suggests it is inferior to zeli which clearly had a virologic effect in peds
2. GILD's fusion inhibitor failed in transplant patients, with lack of both virologic or clinical effects, but we know in the few enrolled transplant paitents zeli had a dramatic effect on virology (numbers admittedly very small), and it suffers from all the drawbacks of fusion inhibitors including high levels of drug resistance
3. The paitents in the failed standard risk adult study for zeli were clearly already improving at enrollment as the total symptom score AUC in the trial for PBO was very low at 62.5. As a basis of comparison TSS was 256 in the same paitent population in the challenge study because you can capture symptoms before peak. The duration of illness in the challenge study was only 5.45 days, so otherwise healthy adults clear illness in under a week on average even when you get a very early diagnosis in a controlled setting
4. The data in older high risk adults suggests that duration of illness is more like 15-16 days on average, and a significant proportion are hospitalized. For example in this trial 16% of older adults with comorbidities were hospitalized (https://www.nejm.org/doi/10.1056/NEJMoa043951?url_ver=Z39.88-2003). In the GSK vaccine trial 2 patients were hospitalized out of 47 cases of RSV LRTI, but there were alot of adults enrolled between ages 60-75 without comorbidities, while the zeli HR trial limits the number of patients 65-75 to enrich for much older patients (over 75) and / or those with comorbidities. So you have to think 5% to low double digit percent patients end up hospitalized, so there is a chance the zeli trial, while clearly not powered on hospitalization, can show a trend if say 5-6 of the 90 placebo patients end up hosptialized versus 2-3 of the 90 patients in the tx arm. It is worth noting that PFE was planning on a large 2715 patient adult HR phase 3 for sisunatovir with hospitallization as the primary endpoint before they ran into difficult with the program (including DDIs) and had to scrap the study
5. Ziresovir, ark's Fusiion inh, showed no virologic effect on day 2 and a minimal .4 log difference day 3 while Zeli was closer to a log day 3 in peds so clear suggestion zeli acts faster and is more active overall (1.4 vs .6 log at day 5) than ark bio, which was able to tease out a clinical effect in peds using their symptom tool
6. JNJ's fusion inhibitor similarly showed very modest antiviral effects in peds compared with zeli https://link.springer.com/article/10.1007/s40272-024-00625-x
But more than anything the much longer duration of illness in the literature in the high risk adult population suggests a much greater window to see an effect on symptoms, and Zeli clearly appears active, giving me a fairly high confidence in the upcoming adult HR readout. I would give it 70% chance of a positive readout of at least a 1 day improvement in duration of symptoms, and a 30% chance of very good efficacy with a 2 day improvement or more in symptoms and / or a trend in hospitalization.
DC15
3 days ago
We do not know that the ASK-1 program "failed" because it was just sort of dropped. I suppose it could be considered a program which failed to mature. I wish I knew more about why it was dropped. We were seeing all of the specificity and precision maps, then the program disappeared from the pipeline and was not mentioned thereafter.
If I knew more about why the ASK-1 program was dropped, then I would have more information upon which to judge the likelihood of success in the KIT and STAT 6 programs.
I would say that Enanta has suffered some business development setbacks. They announce molecules they feel are best in class, but then are unable to put them on a launch pad.
If it is not a business development problem, then it could be a chemistry problem, but when programs are dropped I don't think we learn enough about why they are dropped so there is a difficulty in whether to know if there is a business development problem or a chemistry problem.