By Doug Macron
Silence Therapeutics this week provided an update on its pipeline and planned restructuring, having recently closed a previously announced stock offering that raised nearly $10 million.
With the cash infusion, Silence said, it is now planning to move its phase I cancer drug Atu027 into another clinical trial and submit a regulatory filing to the US Food and Drug Administration to begin human testing of a second oncology candidate next year.
Additionally, Silence said that it will continue development of an acute lung injury drug, despite having previously suggested that it will only advance the compound with a partner.
Though one of the higher profile pure-play RNAi drug companies, Silence has been struggling as of late under the cost of maintaining operations in three different countries, and had expected its cash position to last only into the third quarter of this year. Founded when the UK's SR Pharma acquired Germany's Atugen in 2005, Silence acquired California-based Intradigm in 2009 (GSN 12/17/2009). As a result, the firm had its headquarters in London, its research and development efforts ongoing in Berlin, and its corporate development and intellectual property activities in Redwood City, Calif.
In late 2010, Silence announced that it was in talks with an unnamed party about a merger or acquisition deal, but the negotiations ultimately fell through because the offers made were not “sufficiently compelling … in the context of the continued success of the company” (GSN 2/10/2011).
Without a suitor, Silence eventually determined that it would trim costs through a restructuring since “the geographical diversity of the group creates considerable operational difficulties, as well as increased operating costs,” Silence CEO Phil Haworth, who will be stepping down from the firm when a replacement is found, said in April.
As a result, Silence began shutting down the California location. The company also launched an effort to raise money through the sale of roughly 325.4 million newly issued shares at 2 pence per share. Expected to raise between £5.5 million ($9 million) and £6.5 million, the stock sale ultimately grossed £5.9 million ($9.7 million), which is expected to extend the company's operational runway to around mid-2012, Silence said.
As the closing of the California facility moves toward an expected third-quarter completion date and with the cash infusion completed, Silence said it is now on “substantially improved financial footing” and is capable of meeting a number of R&D goals including the completion of on ongoing phase I study of Atu027 and the start of a follow-on trial.
The drug is a blunt-ended siRNA targeting the protein kinase PKN-3, which is associated with cellular morphology and locomotion in endothelial and cancer cells, and is currently being tested in a phase I study of patients with advanced solid tumors.
Interim data from the trial are slated for presentation later this month at the annual meeting of the American Society of Clinical Oncology. According to a poster abstract published by ASCO last month, the drug appears to be well tolerated, with a subset of patients showing disease stabilization, and one breast cancer patient showing a regression of liver metastases (GSN 5/26/2011).
Silence said this week that the phase I study will conclude in the second half of this year, with a phase Ia/IIb trial in patients with specific tumor types beginning in the middle of next year. The company added that it aims to find a partner for the drug in 2012.
Meanwhile, Silence is advancing a second cancer drug, Atu134, through its preclinical pipeline with the goal of filing an investigational new drug application with US regulators in the second half of next year.
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Like Atu027, Atu134 is delivered using Silence's proprietary AtuPlex liposomal delivery technology, but its siRNA payload targets CD31 in the endothelium of tumors. With the stock sale completed, Silence is preparing to start manufacturing the materials needed to complete final preclinical toxicology studies on the drug, with an eye to filing the IND and starting phase I testing in the second half of 2012.
Getting a second chance in Silence's pipeline is its preclinical acute lung injury treatment Atu111. Unlike the company's other therapeutic candidates, this agent uses a newly developed lung-delivery technology called drug-assembling cholesterol complex, or DACC, to deliver siRNAs against an undisclosed target.
Data from the program have been promising, showing that the DACC delivery technology is capable of achieving sustained knockdown of up to three weeks in the lung endothelium. However, earlier this year Silence said that it planned on only using the proceeds of the stock offering to advance the oncology drugs, leaving Atu111 as an “attractive opportunity for potential pharmaceutical partners.”
The company this week reiterated its expectation that the drug will garner attention from potential allies, but said that it will now “advance preclinical development … for systemic delivery to the lung for the treatment of pulmonary disease.”
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