Phase 3, two-part trial of weekly idursulfase beta (0.5 mg/kg) in treatment‑naïve male patients with MPS II showed marked improvements in 6‑minute walk distance, large reductions in urinary glycosaminoglycan excretion and liver/spleen volumes, with a satisfactory safety profile compared to a historical placebo cohort.
0:15Welcome to Base by Dace. Today we're going to be exploring some really interesting clinical research, looking at a treatment for a rare genetic condition called mucopolysacerdosis 2nd or MPS 2. You probably know it better as Hunter Syndrome.
0:28That's right. And our discussion today is grounded in a specific phase 3 study, a really key clinical trial, which was just published in genetics in medicine this year, 2025. The lead author on this was Young Basson, working with several colleagues.
0:42Okay, so Hunter Syndrome and PS2. Maybe just a quick refresher. It's a serious genetic condition, X-linked, meaning it mostly affects boys. It's caused by the body not having enough of a crucial enzyme, I dorinate 2 sulfitase or IDS for short.
0:57And without that enzyme, these complex sugar molecules, uh, glycosaminoc lycens, or gigs. They just build up inside the cells, right? Exactly. They accumulate in lysosomes, which are like the recycling centers of the cell.
1:09And this buildup causes progressive damage across many systems, the skeleton, facial features, joints. Internal organs too, like the liver and spleen getting enlarged. Yep. And respiratory issues, heart problems, and there can be neurological involvement too, although it varies quite a bit between individuals, there are more severe and more attenuated forms.
1:29Right. And for a long time, treatment was mainly just managing symptoms. It was. But then came enzyme replacement therapy, ear art. That was a huge step forward. The idea is simply to provide a working version of that missing IDS enzyme intravenously.
1:43And we've had one ERT available for a while, either Sulface, brand name, Elaprace. Correct. Approved back in 2006. Studies showed it helped reduce those urinary jig levels, shrank enlarged organs, and improved exercise capacity, often measured by something called the 6 minute walk test, the 6 MWT.
2:01Okay, so this new paper is looking at a different version of that enzyme. Essentially, yes. It's called Idrisulface Beta, also known as Hunter S. It's another recombinant lab-made version of the IDS enzyme.
2:12It was actually approved in Korea back in 2012. And what did earlier research suggest about this hydrosulface beta. Was it expected to be similar or different? Well, the preclinical work in mouse models looked promising.
2:23It showed the expected JAG reduction in organs, and interestingly, at higher doses in those mouse studies, there is maybe even a hint of benefit for CNS damage. Interesting. And inhumans. There was an earlier phase 12 study.
2:37It suggested that either self-face beta, given weekly at either 0.5 or one. 0 millige kilogram, might actually perform a bit better than the standardizer cell phase dose, especially looking at those urinary jags and the 6 minute walk test.
2:50So this phase 3 trial we're discussing today. Its main goal was what? To confirm that efficacy. Precisely. To formally demonstrate the efficacy and safety of idrosulface beta, specifically using the .5 milligram per kilogram weekly dose, which is kind of the standard comparison dose.
3:07Okay. And you mentioned something about the control group earlier. They didn't use a regular placebo group. Right. That's a really important point. Because MPS 2 is so rare. And because there's already an effective treatment available under sulfase, it raises ethical questions about giving some patients a placebo.
3:23Makes sense. You wouldn't want to withhold working treatment. Exactly. So instead, they used what's called a historical placebo group. They took data from the placebo arm of a previous, well conducted trial of eider sulface, the TKT 024 study, to serve as the comparison.
3:39That's a clever workaround for a rare disease trial. So how did they actually structure this study, then it sounds a bit complex. It had 2 main parts run sort of sequentially. Part one was randomized and double blind.
3:52Half the participants got Iger sulfase beta. The other half got the existing eider sulfase. This ran for 52 weeks. Okay, double blind. So neither patients nor doctors knew who got which, and the goal of part one.
4:04The primary goal of part one wasn't necessarily to prove one was better than the other head-to-head right then. It was more about validation. They needed to check if the results they were seeing in their age or Sulface group, particularly on that 6 minute walk test, were comparable to the results from the historical eider Sulface group.
4:19Ah, I see. So, before they could compare Eider Solty's beta to the historical placebo, they 1st had to show that their current Idrosulfies group behaved like the historical Idrosulfies group, sort of like calibrating the comparison.
4:30That's a good way to put it. Yeah. They needed to establish that reproducibility. And once they did that. Once they confirmed that the 6 minute walk test results were indeed comparable, they initiated part two.
4:40This part was open label, meaning everyone knew they were getting idrosulfas beta, and they enrolled additional participants who all received idroselfas beta for 52 weeks. Okay, so more people getting the new drug and then for the main analysis.
4:55They pooled the data. They took everyone who received outer sulfice beta from both part one and part 2 and compared that combined group against the data from the historical placebo group. Got it. Who were the people in this trial?
5:06The participants. They were all male individuals diagnosed with MPS 2, aged 5 years or older. Crucially, they had to be treatment naive, meaning they hadn't had ET before. And they had to show clinical signs.
5:17Yes, things like enlarged liver or spleen, the characteristic skeletal issues known as disestosis multiplex, heart valve problems, airway obstruction, plus biochemical conformation of low IDS enzyme activity.
5:32Any key exclusions. People who'd had prior ERT or certain major procedures, like a hematopoietic stem cell transplant, were excluded. And importantly, for this specific study, all the participants enrolled were Asian.
5:46That's interesting. We should come back to that. And the treatment itself was a weekly 5V infusion for a year. Yep. Either eider sulface beta or eider sulface at that .5 milliga kilogram dose, giving intravenously each week for 52 weeks.
5:59Okay, let's talk endpoints. What were they measuring to see if it worked? You mentioned the 6 minute walk test? That was the primary one. The main thing they looked at was the change in the distance walked in 6 minutes from the start of the study to week 53.
6:11It's a measure of functional capacity. And secondary measures. Quite a few. Those urine jag levels, we talked about total jags, and also the specific types, Heprin sulfate, HS, and dermatin sulfate, DS.
6:23They measured liver and spleen volume using MRI, lung function using absolute forced vital capacity, or FEC from spirometry, and they looked at heart function with echocardiograms. Makes sense, hitting all the key affected areas, and safety.
6:37What do they track? Standard safety monitoring. All treatment emergent adverse events, or AEs. They paid special attention to acute AEs, things happening within 24 hours of an infusion, like allergic reactions rash, hives, breathing issues.
6:51Also, adverse drug reactions, ADRs, thought to be related to the drug, and any serious adverse events, SAEs. And immune response. Antibodies. Yes, immunogenicity was key. They measured anti-drug antibodies ADAs.
7:06If a participant tested positive for ADAs, they then checked if those antibodies were neutralizing antibodies. Nabs, the kind that could potentially block the enzymes' activity. They also look specifically at persistent nab positivity, meaning nabs were detected consistently over time.
7:21And pharmacokinetics PK, how the drug moves through the body. They took blood samples to measure drug concentration levels using an Elisa method and analyzed that data to understand how the drug was absorbed, distributed, and eliminated.
7:32Okay. So the big comparison was the pooled Idrosol is beta group versus that historical placebo data. How do they crunch the numbers? First, that validation step in part one. They checked if the mean change in 6 MMWT for their eider sulface group fell within the confidence interval of the historical eider sulface group.
7:51It did, which allowed them to proceed. Right. And for the main comparison. They pulled the Eider Sulphase beta participants from parts one and two, giving them a group of 24. They compared their mean change in 6MWT to the mean change in the historical placebo group, which consisted of 32 participants and had shown only a 7.3 meter improvement.
8:12And the statistical test. They used a one sample tie test. Basically, they needed to show that the lower bound of the 95% confidence interval for the improvement scene with ider selfies beta was clearly above that 7.3 meter mark from the placebo group.
8:26That would demonstrate statistical superiority. They also did sensitivity analyses using other methods. All right, let's get to the results then. What did they find? Did Idersulfase beta work? Yes, the primary endpoint was clearly met.
8:39The pooled idrosulface beta group showed a mean improvement in their 6 minute walk distance of 62.2 meters over the year. Wow, 62.2 meters compared to just 7.3 in the historical placebo? Exactly. A really substantial difference.
8:52The statistical significance was very strong, P less, then .0001. It represented about an 18% increase in a walking distance for the treated group. The analysis confirmed superiority over placebo. That sounds like a clinically meaningful improvement in function.
9:07What about the secondary endpoints? Gags, organ size? Similar story there? Really significant improvements compared to placebo. Urine total gags decreased by over 71% on average in the Adersulphase beta group, whereas they actually increased by about 21% in the placebo group over the same period.
9:24Huge difference, and liver and spleen. Also significant reductions. Liver volume decreased by about 27% and spleen volume by about 26% with eider sulface beta. In the placebo group, these organs basically stayed the same size or got slightly larger, again, highly statistically significant results.
9:41So clear evidence is getting into the tissues and reducing that jag storage. What about the lung function, the FDC? That one was interesting. There was no statistically significant difference in the change in absolute FEC between the Eider Sulface beta group and the historical placebo group.
9:55Any ideas why? The authors suggest a couple of possibilities. One, many participants were children or adolescents still growing, so their FEC would naturally increase anyway, potentially masking a treatment effect.
10:08Also, they noted some issues with participants, especially younger ones, not being able to perform the spirometry test reliably or consistently which could have affected the data quality. Right. Those tests can be tricky to perform perfectly.
10:21Okay, and what about that direct comparison from part one? Eider sulfase beta versus the standard isosulface. In that head-to-head part of the study, there were no significant differences between hydrosulface beta and hydrosulface for the primary endpoint, the 6MWT change, or for the reduction in total urine gags or heparin sulfate.
10:41So pretty comparable on the main measures. Mostly, yes, but there was one difference they highlighted. Eider Sulface beta led to a significantly greater reduction in the levels of urine dermatin sulfate, DS, compelled to idrosulface.
10:53Interesting. A specific gig component. Okay, let's shift to the immune response. You said antibodies were common. Yes. Anti-drug antibodies, ADAs, developed in almost everyone, 96% of the Iderselface beta group, and 100% of the Iderselface group in part one.
11:08That's quite typical for ARTs. So the key is whether they're neutralizing antibodies, the nabs. Exactly. And here's where a potentially important difference emerged. While many patients develop nabs, at least once, the rate of persistent nab positivity, having them consistently, was significantly lower in the idersulface beta group.
11:26It was about 17% compared to over 62% in the Idrosulfus group in that part one comparison. That's a notable difference. Did having these nabs actually seem to block the drug from working in the hydroselfase beta group?
11:37Based on their analysis, it didn't seem to have a major impact on the key clinical outcomes. When they compared MAB positive versus NAB negative patients within the Idrosulface beta group, there wasn't a significant difference in the improvement in the 6 minute walk test or the reduction in total urine jags.
11:52So even if Nabs formed, the drugs still seem to provide the main benefits. That's what this data suggests, yes. They did note that the reduction in the specific digs, HS and DS was slightly greater in the nab negative subgroup, but the overall clinical ethic C didn't appear significantly compromised by nab status in this trial.
12:11Okay, that's reassuring. Let's talk safety then. Overall picture. The researchers concluded, Idersulface beta has a satisfactory safety profile, generally similar to what's been seen with Idersulface ERT before.
12:22Most side effects were mild or moderate. Any specific reactions stand out? Adverse drug reactions, things considered related to the treatment, occurred in just over half the eider sulface beta participants.
12:33Acute infusion related reactions within 24 hours happen in about 12, 13% of those on eider sulface beta. What kind of reactions were those? Mostly things like rash or hibes. Importantly, these generally resolved by slowing the infusion rate or giving standard medications like antihistamines.
12:49The rate was actually a bit higher, 25% in the smaller selfies group in part one. Were there any serious adverse events, SAEs? Yes, there were a few, and they were considered drug related by the investigators.
13:00In the pooled eider sulface beta group, 24 patients, 2 patients, about 8% had an SAE. One had a splenic infarction, and one had a severe rash. In the smaller itersulface group in part one, 8 patients, 2 patients 25% had SAEs, interestingly, both involved multiple eye problems.
13:20Eye problems. Interesting. Did they look at safety based on the patient specific genetic mutation, their genotype? They did. They grouped patients into genotype one, usually misense mutations, potentially allowing some residual enzyme function, and genotype 2, often more severe mutations like deletions or frame shifts, likely resulting in no functional enzyme.
13:40And did that correlate with side effects? It seemed to. In the eider sulfase beta group, the SAEs only occurred in patients with genotype 2, 0 out of 7 in genotype 1 versus 2 out of 17 in genotype 2. Acute infusion reactions were maybe slightly higher in genotype 2 as well.
13:54This pattern where more severe genotypes might be linked to a higher risk of adverse events, especially in fusion reactions, has been noted in previous idrosulface studies too. Fascinating. So the specific genetic cause might predict risk.
14:07What about basic labs, vital science? No clinically significant changes were reported in lab results, vital signs, ECGs, body weight, or physical exams overall? And just quickly, the pharmacokinetics? Did the drug level stay consistent?
14:21Yes. The PK data suggested that the drugs behavior in the body was stable between the 1st dose and after multiple doses, indicating consistent exposure over time, which is good? Okay, so let's pull this all together now in the discussion.
14:33What's the main take-home message from this phase 3 trial? I think the main message is pretty clear. Idersulphase beta proved itself to be a safe and importantly effective enzyme replacement therapy for patients with Hunter syndrome.
14:45It showed superiority over a historical placebo in improving functional capacity that 6 minute walk test, and also in reducing the underlying pathology, the JAG accumulation shown by urine levels and organ shrinkage.
14:57And his safety profile looked generally manageable. Yes, comparable to existing IRT, though, the potential link between genotype and adverse event risk is definitely something to keep in mind. Now, you mentioned, under selfies beta, is slightly different from miter sulface.
15:10What's the difference chemically or biologically? Right. They're both recombinant human IDS enzymes, structurally very similar, and both work by being taken up by cells via Menos 6 phosphate receptors.
15:22The key difference lies in how they're manufactured. Different cell lines are used. CHO cells for either cellface beta versus a human cell line provider cellface, and different culture media. And that manufacturing difference leads to.
15:35It leads to subtle differences in the glycosylation pattern, the sugar chains attached to the protein. Specifically, itersulface beta seems to have a higher content of something called formal glycine, which is crucial for the enzyme's catalytic activity and potentially faster cellular uptake.
15:52This translates to higher enzymatic activity both in lab tests and potentially in the body. Ah, so a potentially more potent enzyme molecule from a molecule. That's the idea supported by some of the preclinical and in vitro data.
16:04Although, as we saw in the head to head part of this trial, the clinical difference in the main outcomes wasn't huge over one year, except for that dermatin sulfate finding. Let's revisit that historical placeba.
16:15You explain the ethics, but using historical data always has challenges, right? Absolutely. It's not the gold standard of a concurrent, randomized placebo group. But for rare progressive diseases like MPS 2, where an effective therapy exists.
16:29It's often considered an acceptable and necessary approach. The validation step they did in part one, showing their current iter sulface group behaved similarly to the historical one, really strengthens the validity of using that historical comparison.
16:42Okay. And that 62 meter improvement in the walk test. How significant is that clinically? It's considered quite substantial. It reflects better integrated function of the heart, lungs, and musculoskeletal system.
16:52An 18% increase in walking distance likely translates to a real improvement in patients' ability to perform daily activities and maintain mobility. It's also notably larger than the percentage improvements seen in some of the earlier editor cell face trials.
17:06Makes sense. And the lack of FEC improvement we touched on the potential reasons, the age and compliance issues. Yeah, it's a bit inconclusive from the study. However, the fact that the walk test did improve so much, suggests the overall cardio respiratory function probably did get better, even if the FVC measurement didn't capture it perfectly here, producing liver size might also help breathing by allowing the diaphragm more room to move.
17:32Right. The organ size reduction itself could have indirect benefits, and the J reductions were very clear. Extremely clear. Shows the enzyme is doing its job systemically, clearing out that accumulated material from organs prone to storage, which should prevent further damage and enlargement.
17:48The percentages of reduction were quite similar to what's been reported for iodrosulface previously. Now, you mentioned the participants in this trial were all Asian, whereas the historical placebo group was mostly white.
18:00Could ethnic differences have played a role in the results. That's a fair question. However, the efficacy results seen here with eider sulface beta are quite consistent with the magnitude of effects seen in previous iversulface trials conducted in predominantly white populations.
18:15This suggests that at least for these key outcomes, there probably aren't major ethnic differences in response to this type of ERT. Other studies across different nationalities support this too. Okay And the immunogenicity, lower persistent nabs with idrosol phase beta, but nabs didn't seem to blunt the main clinical effects anyway.
18:35That's the key takeaway on immunogenicity from this study. While ADAs were common, the lower rate of persistent nabs is interesting and potentially advantageous, although the clinical relevance needs more study.
18:46Most importantly, for eider sulface beta in this trial, nab formation didn't seem to negate the improvements in walking distance or overall jag reduction. And the safety link to genotype. Yeah, that reinforces findings from other studies.
18:59It suggests that patients with more severe mutations, genotype 2 might be inherently more prone to experiencing adverse events, particularly infusion reactions when starting to eat. It highlights the potential value of genotyping for risk stratification.
19:13So, wrapping up the conclusions. What's the bottom line? The bottom line from the paper is that iter's self-face beta is a safe and effective eat option for MPS 2. It successfully addresses key somatic or non-neurological aspects of the disease by replacing the deficient enzyme activity.
19:30What are the main implications for patients and doctors? Well, it provides another proven treatment choice. It confirms the benefits of 8 for core physical problems in Hunter Syndrome. The immunogenicity findings are quite encouraging and suggesting nab impact might be limited, at least over one year.
19:46And the genotype finding might help in counseling patients about potential side effect risks. And limitations we should keep in mind. Sure. The sample size, while reasonable for rare disease, is still relatively small, especially for detecting rarer side effects.
19:59The FEC data limitations we discussed, and the reliance on a historical control group while justified isn't quite the same as a concurrent placebo. So where does research go from here? Definitely need longer-term studies to confirm these benefits hold up over many years and to monitor long-term safety.
20:17More investigation into that genotype safety correlation with larger numbers would be valuable, and assessing the impact, if any, on neurological aspects, remains a critical area, as the study focused on somatic outcomes.
20:30Understanding the why behind the different nab rates could also be informative. Well, that's our analysis of this important clinical trial on hydrosulface beta for Hunter syndrome. It's really fascinating to see the progress being made in developing and refining therapies for these challenging rare conditions.
20:44Absolutely. And maybe a final thought for you, the listener. Consider how these seemingly small differences, in manufacturing complex biologic drugs, like the glycosylation patterns we discussed, might actually have downstream effects not just on how well the drug works, but potentially on how the patient's immune system reacts to it, and maybe even linking back to their specific underlying genetic mutation.
21:06It's all interconnected. This analysis was based on an open access article published under a CCBY 4.0 license. You can find the DOI and a link to the license details in the description.
