Positive Results Achieved from Interim Analysis of ATL1103 Phase II Trial

Dec 23, 2013, 07:15 ET from Antisense Therapeutics Limited

TOORAK, Australia, Dec. 23, 2013 /PRNewswire/ -- 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.

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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.


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."

ATL1103 Phase II trial is a randomised, open-label, parallel group study of the safety, tolerability, pharmacokinetics and efficacy of two subcutaneous dosing regimens of ATL1103 in 24 adult patients with acromegaly dosed with ATL1103 for 13 weeks (3 months) with two months of follow up. Two ATL1103 dosing regimens are being tested (a) 200 mg 3 times in the first week then once weekly thereafter (200 mg/week) or (b) 200 mg 3 times in the first week then twice weekly thereafter (400 mg/week). The primary endpoints or main purposes of the trial as listed on the trial protocol are (i) to evaluate the safety and tolerability of ATL1103 in patients with acromegaly, and (ii) to evaluate the single dose and multiple dose pharmacokinetic profiles of ATL1103 via the subcutaneous route in patients with acromegaly. A secondary, but important endpoint that is also on the trial protocol is the evaluation of ATL1103's effect on serum insulin like growth factor I (IGF-I) levels in patients. The secondary endpoint is the average percentage reduction in serum IGF-I levels at the end of treatment compared to baseline levels for each of the two dosing regimens used in the Phase II study.

ATL1103 is a second generation antisense drug designed to block growth hormone receptor (GHr) expression thereby reducing levels of the hormone insulin-like growth factor-I (IGF-I) in the blood and is a potential treatment for diseases associated with excessive growth hormone and IGF-I action. These diseases include acromegaly, an abnormal growth disorder of organs, face, hands and feet, diabetic retinopathy, a common disease of the eye and a major cause of blindness, diabetic nephropathy, a common disease of the kidney and major cause of kidney failure, and some forms of cancer. Acromegalic patients are known to have significantly higher blood IGF-I levels than healthy individuals. Reduction of these levels to normal is accepted by clinical authorities as the primary marker of an effective drug treatment for the disease. GHr is a clinically validated target in the treatment of acromegaly. In the case of diabetic retinopathy, published clinical studies have shown that treatments producing a reduction in IGF-I levels retarded the progression of the disease and improve vision in patients. Scientific papers have been published on the suppression of blood IGF-I levels in mice (Tachas et al., 2006, J Endocrinol 189, 147-54) and inhibition of retinopathy in a mouse retinopathy model (Wilkinson-Berka et al., 2007, Molecular Vision 13, 1529- 38;) using an antisense drug to the GHr. ANP have also reported that ATL1103 suppressed circulating levels of IGF-I in primates. In a Phase I study in normal volunteers, ATL1103 was assessed as being safe and well tolerated, while also demonstrating a preliminary indication of drug activity including suppression of IGF-I and the target GHR (growth hormone binding protein) levels.  ATL1103 commercialisation is covered by patents to at least 2024, with the potential for extensions up to 2029 in some countries and 2030 in the US.

Acromegaly is a serious chronic life threatening disease triggered by excess secretion of growth hormone (GH) by benign pituitary tumours. Oversupply of GH over stimulates liver, fat and kidney cells, through their GH receptors, to produce excess levels of (IGF-I) in the blood manifesting in abnormal growth of the face, hands and feet, and enlargement of body organs including liver, kidney and heart. The primary treatments for acromegaly are to surgically remove the pituitary gland and/or drug therapy to normalize GH and serum IGF-I levels. In North America and Europe there are approximately 85,000 acromegaly patients with about half requiring drug therapy. Cost of drug therapy ranges from approximately A$30,000/annum to over A$60,000/annum depending on the treatment.

Antisense Therapeutics Limited (ASX: ANP) is an Australian publicly listed biopharmaceutical drug discovery and development company. Its mission is to create, develop and commercialise second generation antisense pharmaceuticals for large unmet markets. ANP has 4 products in its development pipeline that it has in-licensed from Isis Pharmaceuticals Inc., world leaders in antisense drug development and commercialisation - ATL1102 (injection) which has successfully completed a Phase II efficacy and safety trial, significantly reducing the number of brain lesions in patients with multiple sclerosis, ATL1103 a second-generation antisense drug designed to block GHr production and thereby lower blood IGF-I levels and is in clinical development as a potential treatment for growth and other GH-IGF-I disorders, ATL1102 (inhaled) which is at the pre-clinical research stage as a potential treatment for asthma and ATL1101 a second-generation antisense drug at the pre-clinical stage being investigated as a potential treatment for cancer.

Contact Information:
Website: www.antisense.com.au 
Managing Director: Mark Diamond +61 (3) 9827 8999
USA Investor/Media: Joshua Drumm +(1) 212 375 2664; jdrumm@tiberend.com 
Australia Investor/Media: Simon Watkin +61 (0)413 153 272; simon@marketconnect.com.au

SOURCE Antisense Therapeutics Limited