Eugene Sullivan
Analyst · Goldman Sachs
Thank you, Will, and good morning, everyone. I'm pleased to share with you the data we have produced to date from each of our 2 programs that have been running in parallel for TPIP. I will start with the top line results from our recently completed Phase II safety study of TPIP in patients with pulmonary hypertension associated with interstitial lung disease, which were posted to our website this morning.
I will then walk through the most recent blended blinded data from our ongoing Phase II efficacy study of TPIP in patients with pulmonary arterial hypertension. Let's begin with PH-ILD. This study originally targeted an enrollment of 32 patients but was over-enrolled with 39 patients. The study utilized a 3:1 randomization scheme and as a result, 29 patients were randomized to receive TPIP and 10 were randomized to receive placebo for the 16-week treatment period.
The maximum TPIP dose allowed in the trial was 640 micrograms once daily. As a reminder, a TPIP dose of 640 micrograms contains roughly 60% more treprostinil as compared with the total daily dose of the current market-leading treprostinil dry powder product, which is dosed 4 times daily. Patients were titrated up to their maximum tolerated dose over the course of the first 3 weeks of treatment with a final dose increase allowed at the 5-week visit.
Patients were not permitted to increase their dose for the remaining 11 weeks of treatment. Participant demographics and baseline characteristics were generally well balanced between study arms. However, higher percentage of female participants were randomized to TPIP arm at 31% versus the placebo arm at 20%. Also, on average, patients in the TPIP arm of the study required one additional liter per minute of supplemental oxygen at baseline.
The study's primary objective was to evaluate the safety and tolerability of TPIP in patients with PH-ILD, including assessments of oxygenation at rest and during exercise.
Let's begin with tolerability. Among patients in the TPIP arm, 79.3% were successfully able to reach the maximum dose of 640 micrograms by week 5 compared with 100% of those taking placebo. If we look at the patients who were able to reach at least 480 micrograms by week 5, nearly 90% of TPIP patients were able to achieve that threshold. This indicator of the tolerability of TPIP in this patient population is very encouraging, given the relatively short titration period included in the trial, and considering the severity of the underlying disease process. Of note, while we adopted a titration period of 5 weeks for the purposes of this trial.
In clinical practice, a more prolonged titration period could be applied, which may allow for even more patients to reach higher doses. Additionally, we saw that patients taking TPIP were less likely to experience a treatment-emergent adverse event that would lead them to discontinue the treatment with 13.8% of patients in the TPIP arm experiencing such an event compared to 30% in the placebo arm. We consider a higher treatment discontinue rate in the placebo versus treatment to be very noteworthy.
In terms of overall safety, 93% of patients in the TPIP arm experienced any adverse event, which was similar to the 90% of patients on placebo, and 20.7% of TPIP treated patients experienced a serious adverse event compared to 40% of placebo-treated patients. Zero patients in either arm experienced a serious adverse event that which had to be related to study drug.
There were 4 deaths in the trial including 6.9% of patients randomized to the TPIP arm, and 20% of patients randomized to placebo arm. All deaths in the trial were related to disease progression or comorbid causes and none were attributed to study drug.
One of the key reasons to conduct an initial safety trial in this population was to confirm that inhalation of TPIP would not negatively impact oxygenation. Therefore, we were very pleased that we saw no worsening of oxygen saturation levels at rest, and no increase in the use of supplemental oxygen for patients taking TPIP.
Additionally, we also measured oxygen saturation continuously during and after the 6-minute walk test to capture the lowest blood oxygen levels reached during that entire period of time, and found no meaningful differences between the TPIP and placebo arms on that measure, which is what we had hoped to see. I do want to note that we did see a slight decrease in oxygen saturation from baseline levels when measured after the 6-minute walk test with the TPIP arm showing an absolute decrease of 8% compared to placebo patients who saw an absolute increase from baseline of 1%.
However, I would emphasize that there was no standardization in the trial regarding the timing for when that measure was recorded following exercise. So there is likely to be significant variability in that data point. As a result, we believe that the values reflecting the resting and the lowest oxygen saturation are the best indicators of the effect of the drug on oxygenation. Although we were previously not sure whether we would have any results from our exploratory endpoints in this study to share with you at the time of the top line safety readout, I'm pleased to report that we do have several of those data points available to share today.
Let me begin with the 6-minute walk distance. We were pleased to see a 30-meter improvement compared to placebo at week 16 in patients taking TPIP using the study's prespecified analysis for that comparison. However, let me provide a note of caution on overinterpreting that exploratory endpoint in a study this small. As we have said many times in the past, 6-minute walk distance often includes a substantial amount of variability as emphasized by the wide confidence intervals we see in this data set. As expected in a study this small, the improvement in 6-minute walk distance did not approach statistical significance.
On NT-proBNP levels, the TPIP arm showed a slight improvement from baseline and the placebo group showed a slight worsening. However, the difference between groups was not meaningful which is to be expected in this small study.
Finally, in this study, we measured events of clinical worsening which was defined as a hospitalization due to a cardiopulmonary indication, lung transplantation, death from any cause, or a decrease in 6-minute walk distance of 15% or more from baseline. To be clear, we did not expect to see a signal on this exploratory measure given the study's small size. However, clinical worsening events were shown to be more common in the placebo arm with 50% of placebo-treated patients experiencing such event compared to 10.3% of TPIP treated patients. This difference produced a nominally significant p-value of 0.0164.
We are extremely encouraged and pleased with today's results and look forward to sharing more of the pharmacokinetic and additional safety and exploratory endpoints from the study at an upcoming medical conference later this year.
Importantly, based on today's data, we intend to move this program forward to Phase III aiming to initiate a global study in 2025.
Now let me spend a few moments providing you an update on our ongoing Phase II trial of TPIP in patients with pulmonary arterial hypertension. The trial is progressing as expected now with well more than half of the target enrollment achieved. In March, the second Data Monitoring Committee meeting was held to review the safety data from this trial and the committee's recommendation was to continue the trial without any changes.
In regard to dosing, among the first 43 patients in the trial to complete their 5-week visit, 79% were able to reach the maximum dose of 640 micrograms or matching placebo, which is consistent with our last update and is very encouraging.
We have already received the necessary regulatory approvals in 10 of 17 countries where the study is being conducted to amend the protocol in the open-label extension of this trial to allow for even higher dosing up to a maximum of 1,280 micrograms once daily. We are excited about what these higher doses could potentially mean for patient outcomes.
Today, I would like to share an update on the blinded efficacy data we have seen thus far in this trial. This update includes data from the first 44 patients randomized in the trial. Of those patients, 4 discontinued the trial prior to completion, leaving 40 patients who completed the full 16-weeks of treatment. As a reminder, this trial is randomized 2:1, so roughly 2/3 of the patients will be receiving TPIP and 1/3 will be on placebo.
Starting now with the blinded data on pulmonary vascular resistance or PVR. Among the 40 patients who completed the study as of the data cutoff, the mean percentage reduction in PVR at week 16 compared to baseline is 19.9%. This observed reduction in PVR is comparable to the best clinical results produced with prostanoid treatments in the past, despite the fact that our result for TPIP is a blend of treated and placebo patients. What is equally encouraging is that we continue to see patients in the study who experienced dramatic improvements in PVR.
We're also excited by what we are seeing on 6-minute walk distance, which is another key efficacy measure for these patients. On average, across these 40 patients, including the TPIP and placebo arms of the trial, improvement in 6-minute walk distance from baseline was 43 meters. As I mentioned a few moments ago, 6-minute walk is since is a highly variable measure and especially difficult to interpret on a blinded basis, but we are nonetheless encouraged by what we have seen so far.
It is worth pointing out that for both efficacy endpoints that I've described today, PVR and 6-minute walk distance. These measures were taken at the end of the dosing interval or nearly 24 hours after the most recent dose. This was designed intentionally to highlight the potential durability of TPIP's effect. However, it makes these results more difficult to compare to the other key study of inhaled treprostinil, which reported hemodynamic measures obtained in the period immediately following the dose at the time of the drug's maximum effect. The fact that we are seeing profound effects in some patients in our study, nearly a full day after taking a dose makes us very excited for the potential of this treatment.
As a final reminder, we do not know which of these first 40 patients were taking TPIP in which we're taking placebo. And the numbers I have shared today on PVR and 6-minute walk distance will continue to change as more patient data is generated.
However, we believe today's data supports our view that TPIP has the potential to be a best-in-class treatment for patients with PAH and PH-ILD, combining a potentially differentiated clinical profile with the convenience of once-daily dosing.
Now let me turn the call over to Sara to walk through the detailed financial results from the first quarter.