Antisense ATL1102 final phase 2 DMD results meet primary endpoint and exceed expectations on seconda

Antisense Therapeutics is pleased to advise that the Phase II clinical trial of ANP’s immunomodulatory therapy, ATL1102 for Duchenne Muscular Dystrophy (DMD) has met its primary endpoint confirming the safety and tolerability of ATL1102 for advancement into a potentially pivotal Phase IIb clinical trial.

Importantly, the final trial results have also confirmed the drug’s positive effects on the secondary trial endpoints that assessed the drug’s activity and efficacy including measuring the effects on immune cell numbers in the blood and measuring the participants’ functional capacity as evaluated via Performance of Upper Limb Test (PUL2.0), grip and pinch strength and distal mobility (using the MyoSet, MyoGrip, MyoPinch and MoviPlate tools, respectively).

Additionally, the Company is very pleased to report that MRI assessment of the upper limb muscles of the patients with DMD has also shown the drug’s apparent beneficial effects in stabilising the fat fraction percentage within the muscles of the forearm (increase in fat levels is another key marker of disease progression in non-ambulant DMD boys). The data shows a stabilisation in the percentage of fat in the forearm muscles and an increase/maintenance of functional muscle mass, which is both outstanding and unexpected for a drug treating the inflammation (and not the muscle dystrophin loss).

Results overview

The primary objective of the ATL1102 trial was to assess the safety and tolerability of 25 mg of ATL1102 administered once weekly (subcutaneous injection) for 24 weeks in nine non-ambulatory DMD participants. ATL1102 was assessed to be generally safe and well tolerated. No Serious Adverse Events were reported with no safety concerns expressed by the Data Safety Monitoring Board. There were no participant withdrawals from the study. The most commonly reported adverse events have related to the subcutaneous administration of the drug, mainly injection site erythema and skin discoloration which were generally regarded as mild and either resolved or were close to resolution at the end of the monitoring period. Overall, ATL1102 demonstrated an excellent safety profile in this trial.

Dr Ian Woodcock, Paediatric Neurologist and Honorary Fellow at The Murdoch Children’s Research Institute, Melbourne and the Principal Investigator of the ATL1102 Phase II DMD trial said, “the study met its primary endpoint showing ATL1102 to be safe and well tolerated with no serious adverse events being reported and no participant withdrawing from the study. With very few treatment options for boys with Duchennes who are no longer ambulant, it has been great to enable the boys to participate in this clinical trial and I am most encouraged by the outcomes of the study”.

ATL1102 is an inhibitor of CD49d expression on certain immune cells (e.g. T lymphocytes). It has been reported in research literature that patients with DMD who have a greater number of CD4+ and CD8+T lymphocytes with high levels of CD49d have more severe and rapid disease progression. ATL1102 is the only drug in clinical development for DMD targeting CD49d and one of a very limited number of treatments being tested in non-ambulant boys with DMD.

In assessing the effects of ATL1102 on immune cell numbers in the blood of participants, the immune cell data has shown a consistency in the mean reductions in the number of lymphocytes including T-lymphocytes (i.e. CD3+, CD3+CD4+, CD3+CD8+ and importantly, those expressing CD49d) measured from baseline to week 8, 12 and 24 (end of dosing) with a rebound of these markers to around starting levels post dosing at week 28. As previously reported, the mean number of CD3+CD49d+ T cells (i.e. mostly CD3+CD4+CD49d+ and CD3+CD8+CD49d+cells) at week 24 is statistically significantly lower vs week 28 (p=0.030 paired T test) suggesting the drug is working through its targeted mechanism of action. We further report that the mean number of NK lymphocytes (CD3-CD16+CD56+) and NK lymphocytes expressing CD49d+ at week 8,12 and 24 is statistically significantly lower vs baseline using a mixed model for repeated measurements (p=0.018), with comparable NK lymphocyte numbers at week 28. This data demonstrates the drug’s positive effects on modulating CD49d+ lymphocytes in the blood during treatment.

As reported in December 2019, the PUL2.0 data showed that 7 of the 9 participants demonstrated either increases or no change in their PUL2.0 scores from baseline over 6 months, with a positive mean change of 0.9 (95% CI: -1.33, 3.11) in this key parameter indicative of disease stabilization. This contrasts to the losses in PUL2.0 reported in the published literature in longer term (1 year plus) studies (Pane et al 2018). Similarly, MyoGrip and MyoPinch assessments using the Myoset system showed a significant improvement in muscle strength compared to the loss of muscle strength reported in the Ricotti et. al. 2016 publication in a similar non-ambulant patient population on corticosteroids assessed over 6 months. MoviPlate data (an assessment of muscle function), has also demonstrated improvements in a majority of the participants with a mean increase from baseline to 6 months of 1.9 points (95% CI: -6.08, 9.85).

Dr Jean-Yves Hogrel, PhD, Director of the Neuromuscular Physiology and Evaluation Laboratory, Institute of Myology, France, a developer of the MyoSet assessment tools stated that “First, I would like to highlight the quality of the data that proves the expertise and dedication of evaluators in following standardised operating procedures. The intra-individual variability is very moderate and reflects this measurement quality. My observations based on the MyoSet data from the study suggest that the patients were generally stable.”

Overall, the study has shown that ATL1102 treatment results in consistent improvements or stabilisation across the different measures of motor function and strength.

In a post hoc analysis of the data, there appears to be a correlation between the individual patient PUL2.0 scores at the end of dosing (week 24) and their week 24 vs week 28 CD4+CD49d+ T cell changes. Of the eight participants with normal starting levels of lymphocytes, six demonstrated either an improvement or maintenance in their PUL2.0 scores and had a ‘rebound’ in the CD4+CD49d+ T cells at week 28, while two of the eight participants who had a loss of PUL2.0 at week 24 did not see a rebound in these cells at week 28 vs week 24. This data suggests that the drug is working through a targeted CD49d mechanism of action with down-modulation of CD4+CD49d+ T cells during treatment providing clinical benefit, with the two patients not responding at 24 weeks, potentially requiring longer and/or higher dosing to see similar effects. While this correlation was only observed with the PUL2.0 disease progression parameter (the expected primary efficacy endpoint for future trials), it is the Company’s view that as PUL2.0 assesses the performance of a large group of muscles of the upper body (unlike Myoset which specifically assesses grip and pinch strength and distal mobility) it is appropriate to draw out this correlation as it may be a helpful future prognosticator of response to therapy.

Importantly the MRI data assessing the fat fraction percentage of the muscles of the dominant forearm of the participants has delivered a further most positive finding with the data showing a slight mean reduction in these levels compared to the significant increases in fat fraction reported in the Ricotti 2016 publication with the comparison showing to be statistically different on some of the MRI parameters. The change in percentage fat fraction from baseline to 24 weeks was (mean (SD); Median) -0.5 (6.6); 1.4 for the central reading and corroborated by the proximal and distal readings (-2.1 (7.1); -0.4 and -5.1 (14.6); 2.0, respectively). Furthermore, the lean muscle area (i.e. non-fat) showed a change from baseline to 24 weeks (Mean (SD); Median) of 13.9 mm2 (SD: 112.5); 5.8 mm2, indicating a maintenance of and possible increase in functional muscle mass. This is a somewhat unexpected but highly encouraging observation for a drug treating the inflammation and not the muscle dystrophin loss (the exon skipping drug’s target).

Dr Valeria Ricotti MD, Researcher and Honorary Clinical Lecturer, Great Ormond Street Institute of Child Health University College London, UK, stated that “Based on the MRI data from the study, the observed stabilisation in the percentage fat fraction with ATL1102 treatment would not be expected in the natural course of disease in DMD even under corticosteroid treatment. Furthermore, the stabilisation of fat fraction percentage combined with the observed maintenance/increase of remaining muscle area is suggestive that ATL1102’s effect could preserve the contractile muscle mass.”

Further data analyses performed by Dr Jean-Yves Hogrel looking at the correlation between MRI results for remaining muscle area (removing the fat fraction) with the results of the MyoGrip assessments for the individual participants has shown a highly significant positive correlation between these measures.

Dr Hogrel stated that “this positive correlation of remaining muscle area (the lean muscle), with grip strength suggests a consistency of the results across the different parameters of muscle structure and muscle force.”

Quality of Life (PedsQL) questionnaires were completed by parents of the younger boys in the study and by two of the teenage boys. Both the teens that completed the questionnaire showed a mean improvement in all the domains; problems of daily activities, treatment management, problems with communication and worry. The results for the younger patients where the parents completed the questionnaire also showed improvements in daily activities and treatment domains but increased problems with communication and worry domains.

Respiratory parameters (FVC and PEF) were also measured. As noted in the December 2019 announcement in our experts’ view the variability in this data makes it difficult to draw any meaningful conclusions on this parameter, which is best assessed in larger studies of 12 months and longer. Nevertheless, with the PEF assessment a slight mean increase in percentage predicted PEF was observed which is consistent with the data observed for the other parameters.

Professor Thomas Voit MD, Director, NIHR GOSH Biomedical Research Centre, UK had this to say about the trial results and the efficacy being observed in this Phase II trial of ATL1102: “The data certainly suggests an overall ‘stabilisation’ in disease progression at the very least which of itself is a very positive clinical outcome. MRI data confirms the positive changes at a muscular/cellular level and supports the observed physical stabilisation/improvements in muscle strength and function. The consistency of positive clinically relevant effects of ATL1102 treatment across muscle measures of structure, strength and function are very pleasing and provide great encouragement for the treatment of non-ambulant patients with DMD”.

The results are highly supportive of the Company’s plans for a Phase IIb clinical trial of ATL1102 in DMD. Scientific Advice meetings held with three European regulatory authorities affirmed the agencies’ general acceptance of the proposed trial efficacy endpoints (PUL2.0, MyoSet), safety monitoring plan, dosing duration (12 months) and the use of higher doses. The Company has made a submission to the European Medicines Agency for Scientific Advice with the results of their evaluation due mid-year, which will then direct the Company on its preparation and submission of its clinical trial application.

Our international Key Opinion Leaders and advisors are encouraged by the results of functional endpoints (physical parameters) that demonstrate strong initial efficacy. Measurements of a number of functional parameters indicate that a majority of the boys experienced either improvement or no deterioration in several upper body measurements. These results compare favourably with data reported in a variety of historical studies of progressive and continuous deterioration in physical function in non-ambulant patients with DMD over time.

Dr Gil Price M.D., ANP’s Consultant Medical Director, said: “In a small study with nine boys of only six months duration at a single low dose we not only achieved our primary endpoint of safety we also i) achieved significance in demonstrating an effect on our secondary endpoint relating to modulation of CD49d; ii) achieved positive outcomes in the important upper body function parameter of the PUL 2.0 test, and finally iii) achieved fat fraction percentage reduction in important upper body muscles. That each of these three effects were observed in an initial study in DMD boys at the lowest dose where we might have anticipated a biological effect is truly surprising and highly encouraging”.

Next steps

The Company is extremely delighted by the trial results and our international experts’ support which provides encouragement to move ATL1102 into a Phase IIb trial.

European Medicines Agency Scientific Advice due mid-year is the next milestone in preparation for submission of clinical trial application for a Phase IIb trial in Europe and UK. The Company is also in the process of preparing submissions for Orphan Drug Designation for ATL1102’s use in DMD in the US and the EU.

As ANP continues to prepare for a Phase IIb, the Company will look to gain a deeper understanding of the drug’s effects. This activity is likely to include further laboratory analysis of retained serum to attempt to tease out more insight on broader inflammatory processes and a deeper analysis of our data against the natural history of the disease with key experts.

In parallel, encouraged by observations of the anti-inflammatory actions of ATL1102, ANP is now also investigating other potential diseases including those that are inadequately controlled with corticosteroids such as other muscular dystrophies and neurological conditions. As previously advised, the Company is working on selecting and prioritising new indications where it is best positioned to leverage its expertise, intellectual property and relationships with clinical experts involved in treatment of those diseases.

Mark Diamond, CEO of Antisense Therapeutics said: “Our focus is to continue planning and to methodically and efficiently move our DMD program through Phase IIb in Europe. There is great interest in the DMD space. As we gain further certainty from the regulatory process on the parameters of the next trial, which may lead to early market approval, we will assess funding and trial management options and also engage in discussions with interested potential partners ahead of commencement of Phase IIb. This will allow the Company to consider the most advantageous way to proceed with the pivotal trial on its own or with a partner. Potential partners’ input into the trial program may also be beneficial for future commercialisation plans. The Company is now in the process of confirming the manufacture of additional clinical supplies of ATL1102 and will provide further updates in due course”.