By Ben Butkus
Scientists from UK-based molecular diagnostics developer Lumora have published a study demonstrating how the company's stem primer technology can in certain cases improve the performance of molecular diagnostic assays based on loop-mediated amplification.
Lumora is betting that the proof-of-principle publication will help attract potential industry partners to develop molecular diagnostic tests that combine the two technologies and Lumora's real-time bioluminescent detection platform, CEO Laurence Tisi told PCR Insider this week.
To that end, the company has initiated discussions with undisclosed candidate partners in the UK and US, and hopes to ink its first molecular diagnostic development deal this year, Tisi added. Meantime, Lumora is continuing to develop its own molecular tests, primarily for HIV viral load monitoring.
Founded in 2002 as a spinout of the Institute of Biotechnology at the University of Cambridge, Lumora initially applied its proprietary core technology platform, called bioluminescent assay in real time, or BART, to the food testing industry.
The BART technique is a reporter system that can detect natural byproducts of nucleic acid amplification in real time and in a closed-tube environment without the use of additional reagents or expensive hardware. Due to the simplicity and low cost of the technique, Lumora has focused on coupling it with isothermal amplification methods, which are similarly simple and inexpensive when compared to PCR-based amplification.
In the past few years, the company began shifting its focus toward molecular diagnostics by testing BART with a variety of isothermal amplification techniques. In May, Lumora said that it raised £1.5 million (about $2.4 million at the time) in a Series B financing to support these efforts (PCR Insider, 5/26/11).
Now, it appears that the company has settled on LAMP as its isothermal amplification method of choice.
"Over the years I've looked at lots of isothermal [amplification methods]," Tisi said. "I still think that LAMP is heads and shoulders above the vast majority of them."
Indeed, LAMP has been shown in multiple studies to have performance equivalent to that of PCR for amplifying target sequences, and several startup and established companies have begun adopting the technology for molecular diagnostics use. It has become especially attractive as a tool to develop assays for point-of-care use or the developing world, primarily due to its low cost and ease of use.
However, according to Lumora, LAMP's uptake has been hindered by challenging primer design: the method requires the design of six loop primers and selection of eight priming sites, with significant restrictions on positioning and orientation.
To address this, the company developed its stem primers, which offer more flexibility in terms of forward and reverse orientation and multiplexing. In addition, as Tisi and colleagues demonstrated in a paper published last month in the International Journal of Molecular Sciences, using LAMP with stem primers in some cases — in their case the detection of target sequences from Clostridium difficile, Listeria monocytogenes, and HIV — increased assay speed, sensitivity, and reproducibility.
"It's all sequence-dependent," Tisi explained. "When you do have sequence variations at a particular locus, it's much better to have them at the 5' end of your primer rather than the 3' end, because primers get upset at mismatches at the 3' end far more than they do at the 5' end."
Lumora's stem primers can be oriented in either direction, "so it helps you navigate bits of sequence where you really want to lay a primer down, but there is a lot of sequence variation," Tisi added. "That's just one example."
HIV is a particularly salient example, and Lumora showed in its paper that a LAMP-based HIV assay using stem primers performed better than the LAMP loop primers. "In fairness, it will be on a sequence-by-sequence basis — sometimes the LAMP primers will be better, and sometimes it will be better to use the stem primers," Tisi said. "We're not saying one is better than the other — it's just about having more options."
Tisi said that Lumora is hoping its expanded primer design toolbox and LAMP expertise will help attract industry partners who are currently developing molecular tests based on LAMP or other isothermal techniques and want to explore ways to improve assay performance.
"We have more than one interest, including a large US and domestic interest," he said. "We're trying to work out the right partner at the moment."
Because the original patents underlying the LAMP technique are owned by Japan's Eiken Chemical, Lumora is making it clear to potential development partners that they would need to license the method from Eiken should they work with Lumora to successfully commercialize a molecular diagnostic assay based on the technique.
"We have a very good relationship with Eiken," Tisi said. "The Eiken technology is basically two patents. There is an underlying original patent, and … they came up with an improvement on it, and that's patent number two, and that's what really makes LAMP fast and commercially viable. Our invention is an alternative to that second invention. In the longer term, when the original LAMP patent [expires], it would mean that we would have freedom to operate using our present invention. At the moment, however, people still need to license the original LAMP patent."
Further, Tisi noted that the recently published paper serves to further validate Lumora's BART technology as an inexpensive but powerful readout method that may eventually become the preferred detection method for LAMP-based assays.
"Previously people thought there was only one option, and their knee-jerk reaction is, 'Oh, you must have to use fluorescence,'" Tisi said. "We showed again that you can use BART to do real-time amplification, and you don't have to use fluorescence and other labels."
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