ANP reports positive interim results from ATL1103 Phase II clinical trial for acromegaly

Dec 23 2013

Antisense Therapeutics Limited ("ANP" or "the Company") is pleased to advise that positive results have been achieved from the interim analysis of a subset of available data from its Phase II clinical trial of ATL1103 in patients with the growth disorder, acromegaly. 

The interim analysis was undertaken on the 8 patients who have completed the full 3 months of dosing at both dosing levels employed in the study. 4 patients received 200 mg of ATL1103 once per week and 4 received the higher dose of 200 mg twice per week (400 mg).

The interim analysis assessed the change (percentage reduction) from each patient's baseline (start of the study) serum Insulin-like Growth Factor-I (sIGF-I) levels to their levels after the completion of dosing with ATL1103. Reducing sIGF-I levels is the primary marker of ATL1103 activity in this trial as acromegaly patients have elevated sIGF-I levels compared to the normal population and furthermore, reduction of sIGF-I to within the normal range in a significant proportion of patients is the goal in Phase III registration trials for acromegaly treatments.

Results

In the 4 patients who received the 400 mg per week dose, ATL1103 reduced sIGF-I levels consistently and by an average (mean) of 30% (range 4% to 48%) at week 14 (one week past the last dose) which is the primary efficacy time point for the trial. sIGF-I levels were reduced by a mean of 38% (28 – 48%) in the 3 patients who had lower body weights (58 - 83 kg at screening) and thereby received a relatively higher dose per kg bodyweight. The one patient showing the lowest sIGF-1 reduction at week 14 had the highest body weight (132 kg at screening). 

At the 200 mg per week dose, no consistent reduction in mean sIGF-I levels was observed at week 14, although some sIGF-I reduction was noted in individual patients.

The time course data (see Figure 1) at the 400 mg per week dose generally shows a progressive rate of reduction in sIGF-I over the dosing period. This is further support for the therapeutic action of ATL1103 observed in this trial and suggests that continued dosing of ATL1103 at the 400 mg per week dose for longer than 3 months could result in additional reductions in sIGF-I.

While sIGF-I levels were substantially suppressed in 3 patients receiving the 400 mg per week dose of ATL1103, their sIGF-I levels did not reduce all the way to normal levels, however this is not surprising considering the study design was not optimised for this endpoint, the small number of patients analysed thus far and that their starting sIGF-I levels (2.4 to 5 times above normal) appear higher when compared to average starting levels of acromegaly patients in larger published clinical studies (e.g. 1.8 times above normal).

To date no patients dosed with ATL1103 have withdrawn from the study nor have any serious adverse events, believed to be treatment-related, been reported. So far, both doses appear to be well tolerated. The positive safety profile to date suggests the drug may be tolerated at higher levels than 400 mg per week and so the Company is considering the prospect of conducting a small add-on study to support the use of a higher dose in Phase III trials for dose escalation in patients with more active disease.

Enrolment into the 24 patient trial is expected to be completed early in the new year. The Company looks forward to the reporting of the statistical analysis of the sIGF-I data from all patients (expected in the second quarter of 2014) and to the potential verification of results achieved in this interim analysis. Other important parameters of drug activity being measured in all patients that will also be assessed at the end of the study include Growth Hormone and Growth Hormone Binding Protein levels along with a more comprehensive assessment of the safety data. Such additional data is expected to give further valuable insight into the safety, activity and mechanism of action of ATL1103 at both dose levels in this patient population.

Chief Investigator for this study, Dr Peter Trainer, Professor of Endocrinology, The Christie NHS Foundation Trust, UK, said: "The reduction in sIGF-I observed at the 400 mg dose in this small number of patients is most encouraging and supports the continuing recruitment of patients into the study and also indicates the potential to explore higher dosages and different dosing schedules in future clinical trials to optimize ATL1103 usage."

Mark Diamond, Managing Director and CEO of Antisense Therapeutics said: "These positive interim results provide us with important indicative data on the efficacy and safety of ATL1103 in treating acromegaly patients. These results are in line with reductions in sIGF-I that could be therapeutically effective in a significant proportion of acromegaly patients and therefore add to our confidence that ATL1103 could become an important drug in the acromegaly market. Based on these interim results, the Company will be following up interest from pharmaceutical companies in partnering the development of ATL1103 for Phase III clinical trials."