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Stanford Spinout Levitas Bio to Launch Magnetic Levitation Cell Separation Platform

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NEW YORK – Levitas Bio, a Stanford University spinout, is preparing the launch of a technology that sounds nearly imaginary: magnetic levitation-based cell separation.

"Unlike anything else out there, when it comes to separating particles, we don't attach or bind anything to the cells," said CEO Martin Pieprzyk. "No dyes, no antibodies. It's touch free." The workflow requires only three steps and can be done in 20 minutes, he added.

The technology uses magnet-induced density gradients to spread out different types of cells and could be used, for example, to separate live cells from dead ones.

Based on data from an automated cell counter, a National Cancer Institute lab, for instance, was able to recover about 75 percent of live cells run through an early-access version of the platform, said Seth Brodie, a senior scientist at the NCI-Frederick cancer genomics research lab. "It's a lot better than what fluorescence activated cell sorting (FACS) can do. You lose tons of cells in a FAC sorter."

The new tech also enables separation of previously inaccessible cell types and avoids the potential for antibodies to confound gene expression in cells by activating them.

Levitas will begin selling its LeviCell platform, including the $90,000 instrument and $90 consumable cartridges, next month with hopes that customers will place it upstream of any number of applications, including cell population analysis, single-cell genomics, and gene editing.

There may also be diagnostic use cases further down the line. "As we start to move into precision medicine, if you can better isolate cell populations, that would inform diagnosis for a particular treatment," said Bill Hyun, director of the Lab for Advanced Cytometry at the University of California, San Francisco and a member of Levitas' scientific advisory board.

Founded in 2017 and based in Menlo Park, California, Levitas Bio is the vehicle for commercializing magnetic levitation technology in the life sciences. Pioneered by George Whitesides, a Harvard University researcher who intended it to replace mass spectrometry, the technology has been used in chemical analysis, for example, for the identification of cocaine.

The company has licensed intellectual property from Stanford and from Brigham and Women's Hospital and counts Stanford Genome Technology Center Codirector and European Molecular Biology Laboratory scientist Lars Steinmetz as one of its cofounders. Stanford Medicine professors Utkan Demirci and Gozde Durmas are also scientific cofounders. Steinmetz is also a cofounder of clinical testing firm Sophia Genetics. In 2015, Steinmetz and Demirci published a paper describing the levitation of single cells in the Proceedings of the National Academy of Sciences.

Levitas Bio has about 12 full-time employees that staff two wet labs and a manufacturing laboratory. The firm closed an $8 million Series A financing round in 2018 led by Decheng Capital.

The key to magnetic levitation is the use of a gadolinium-based magnetic resonance imaging contrast agent. Here, when put in a channel sandwiched between two rare-earth magnets, the contrast agent molecules create a density gradient in which cells or other biological particles can separate from each other.

"It's a matrix that cells are moving through," Pieprzyk said. Where the magnetic field is stronger, the gadolinium particles are more densely packed, crowding out larger entities into the less dense part of the channel. "By controlling the speed at which we control particles, and the magnetic field, we can sort them," he said.

The instrument includes a bright field microscope with two fluorescence channels to image cells as they progress, giving the user a visual read on the populations to select cells of interest.

While the intrinsic magnetic properties of red blood cells can influence behavior in the magnetic gradient, in the majority of cases, the dominant factor is size and density. What's important is that the instrument can adjust the channel to split the sample at a particular point, leading to separation without the perturbations necessary in FACS or bead-based approaches. Levitas Bio is offering instrument presets for certain applications, but researchers should be able to adjust the settings to capture any fraction of the sample they choose.

The firm is not the only one entering the cell separation field with novel techniques. Akadeum Life Sciences is commercializing a bubble-based approach that can potentially be applied to isolating circulating tumor cells in liquid biopsies. That firm has partnered with NanoCellect Biomedical, a San Diego-based firm developing a laser-based cell sorting platform. Also, New Mexico-based BennuBio is developing acoustic technology for rare cell and biological particle isolation.

"The thing that resonates with people is that they finally have a simple way of being able to process primary samples – tissue, needle aspirates, cervical swabs," Pieprzyk said. "The first market that we're commercial in is live cell enrichment. Literally taking a heterogeneous, dirty sample and enriching for fully viable cells."

Pieprzyk said Levitas Bio solves three main issues with legacy sorting technologies, including FACS sorters from Becton Dickinson or Bio-Rad Laboratories or magnetic bead- or column-based assays from Miltenyi Biotec or Thermo Fisher Scientific.

"If you use antibodies or dyes to isolate a live population, you're modifying those cells, they're no longer an unbiased sample," he said. The second issue is with hands-on time. FACS takes three to five hours, he said, and bead-based approaches two to three hours. Levitas Bio's method takes as little as 10 minutes. "In terms of the ability to get samples processed, it's an order of magnitude difference," he said.

Third, and most important, Pieprzyk said, is the ability to work with new cells and biological entities. Levitas Bio can sort fragile cells, including adipocytes and neurons, and can sort cells larger than the FACS limit of about 30 microns, he said. The platform can even sort extracellular vesicles, embryos, organoids, and even a whole organism, specifically Caenorhabditis elegans.

Brodie, the NCI scientist, has been using a version of the Levitas platform for about a year and a half and plans to obtain a commercially-available instrument once launched. In one experiment, his team tried to enrich for chemotherapy-resistant live cells by separating them from dead ones, running the treated cells through the platform and then recovering them in an incubator before passaging them through the process  multiple times. Though the experiment failed due to the fact that the cells would die after numerous passages, the researchers were able to obtain a high percentage of surviving cells after each pass.

"This is sort of plug and chug," Brodie said. "Any other sort of flow cytometry-based method, you need to be an expert to get good results out of." He plans to get an instrument and connect it to the lab's single-cell genomics workflows.

Tim Bushnell, scientific director of the flow cytometry core at the University of Rochester Medical Center, suggested that Levitas Bio's system could be powerful if connected to TotalSeq, a method that employs DNA-tagged antibodies from BioLegend to generate flow cytometry-like data using next-generation sequencing as a readout. "Something like [LeviCell] allows you to prepare your sample for analysis" and helps to prevent dead cells from confounding proteomic or gene expression analyses. Bushnell is a consultant to the firm and said he is in the process of obtaining a system for his lab.  The ability to separate larger cells than other technologies "is going to be very interesting for some of my users," he said.

For now, the LeviCell system can only process one sample at a time. However, the company is planning a high-throughput version of the instrument, capable of working with 96-well plates, to be released next year.

While the LeviCell system could immediately plug in upstream of many genomic analyses, its ability to produce live, unmolested cells could prove extremely valuable to synthetic biology applications, said Hyun, who is also a partner at Genoa Ventures. Genoa is not a Levitas investor and Hyun said he only has "token" shares for his participation on Levitas' scientific advisory board.

Cell therapies, especially autologous and gene-edited cell therapies, need isolation technologies on the front end. "That's a speculative bet" for a potential application of the technology, Hyun said, "but a lot of us are starting to look at and think about it."

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