Isothermal titration calorimetry (ITC), which is a subset of microcalorimetry, is one of the fastest-growing analytical techniques on the market. The technique’s market, valued at $45 million in 2007, is expected to achieve midteen sales growth over the next few years, while calorimetry sales as a whole are only expected to grow in single digits. This impressive growth is driven by the pharmaceutical and biotechnology industries, which has found an invaluable tool to aid them as they push towards new small-molecule drugs and biopharmaceuticals.

The group of companies manufacturing ITC products is not large. The major players in the field are MicroCal, Calorimetry Sciences Corporation (CSC) and TA Instruments. In 2001, Danaher acquired Hart Scientific, whose subsidiary, CSC, manufactures microcalorimetry instruments (see IBO 5/31/01). Last year, Waters acquired Thermometric AB, a Swedish manufacturer of microcalorimetry products, for $2.5 million (see IBO 8/31/06). According to Waters’s first quarter conference call, TA Instruments’ quarterly sales received a five-percentage point boost from

Thermometric’s products.

An ITC system consists of two cells—one for the sample and one for reference—made of a material that conducts thermal energy, surrounded by a casing that prevents heat loss or gain due to external influence. A feedback circuit is established between the two cells. As small quantities of ligand are titrated into the cell containing the sample, small amounts of heat are gained or lost in the sample cell as a result of the thermodynamics of the reaction. These heat changes in the sample cell affect the feedback circuit, as it reacts to maintain an equal temperature in the reference cell, which is filled with water or a buffer. ITC measurements are therefore given as electrical power changes over time.

ITC products have been on the market since the late 1980s. In the words of Rusty Russell, vice president of Sciences at CSC, “since then it’s been a growing technique. If you look in the 80s and 90s, DSC [differential scanning calorimetry] was by far the largest calorimeter market.” All of the companies that manufacture ITC products also manufacture DSC systems, which are widely used in the pharmaceutical industry “Starting in the late 90s and going to the 2000 to 2001 range, it shifted . . . to where ITC is more the driving calorimeter and DSC is seen more as a complement to ITC,” said Dr. Russell.

ITC has a number of benefits. It is easy to perform and requires no ligand or sample labeling. One of the most significant advantages is its capacity to provide a complete energy profile, that is, a full thermodynamic description of a given reaction. In the words of Dr. Russell, “On the ITC . . . we can understand the thermodynamics [of a reaction] and if you understand the thermodynamics of the reaction, then you can begin to understand what’s really happening, the fundamentals of it.” Another element of ITC’s utility, according to Richard Brown, president and CEO of MicroCal, is that “it’s a completely ‘in-solution’ technique and so proteins and small molecules, or proteins and other proteins, are more or less in their native states when the reactions are being done. They’re not immobilized on a surface or immobilized to some other substrate, and so you’re looking at the binding and the reaction of two materials as they would natively occur.” Dr. Russell also noted that this is one of the advantages ITC has over surface plasmon resonance (SPR): “if you take a protein molecule and immobilize it to the surface . . . suddenly you’ve potentially affected the shape of the protein molecule and the way that it’s going to interact.” However, in many cases, such as in the pharmaceutical industry, ITC is used in conjunction with techniques such as SPR, nuclear magnetic resonance and X-ray crystallography. Dr. Brown said that many of CSC’s customers use ITC along with various complementary techniques, but the question of competition arises in those instances when a customer has to choose whether to buy the ITC instrument or the complementary technology first.

The market for ITC is expected to grow due to its use in a variety of academic and industrial applications. For example, ITC is often used for enzyme activity determination in the biotech industry. In chemical applications, ITC can be used to assess the “stability” of volatile compounds, which determines the degree of precaution workers should use when handling them. But the application that has most driven ITC’s market growth is its use in drug development and discovery. “We really have two important industrial markets: the discovery and development of biopharmaceuticals, and the discovery and development of small-molecule drugs,” said Dr. Brown. As Dr. Brown explained, growth in these two segments are driven by distinct dynamics: pharmaceutical companies’ need to keep the pipeline flowing fuels sales to the small-molecule drug sector, while “[o]n the biopharmaceutical side, there are simply so many more organizations—big pharma, big biotech and small biotech—that have an interest in monoclonal antibodies and protein therapeutics and the binding that’s associated with those kinds of molecules. Just the growth in that entire area is driving the growth of our business in that segment.” ITC can give information about the binding affinity of drugs to DNA and RNA, as well as drugs to proteins, and as such it is a highly useful technique for evaluating and reformulating lead compounds.

ITC can also be used for the evaluation and quality control of biopharmaceuticals. A considerable concern in the development and production of biopharmaceuticals is stability. As Dr. Russell pointed out, “you could have a drug that was the greatest drug ever, that did wondrous things, but if it had a shelf-life of two weeks, the FDA would never clear it.” This matter of stability extends to whether or not a given compound will form an aggregate that might be insoluble or provoke an immunogenic response, explained Dr. Brown. Going further, he discussed the different manifestations of stability in biopharmaceuticals: “When people are formulating a biotherapeutic [they’re] looking at the stability of that formulated drug. When they’re developing the processing of that drug, they’re looking at how their process conditions affect the stability of that drug: it’s no good if you have a process that destroys your drug in the midst of that process.” This question of stability also plays an important role in biopharmaceutical development: “what we’ve discovered is that oftentimes people can find dozens or even hundreds of protein variants that are equally potent. So the question is, ‘which one do you bring forward as a new drug if they’re all equally potent?’ . . . [Y]ou bring forward the one that is most stable,” said Dr. Brown.

The manufacturers of ITC systems offer a variety of products for a number of different applications and end-users. MicroCal’s VP-ITC offers three different operation modes, which allows users to adjust the instrument for reactions that produce very small temperature fluctuations. The AutoITC, also from MicroCal, has automated cleaning and cell-loading capabilities; the instrument can run up to 100 experiments in a week unattended. Dr. Brown explained that the primary difference between the two products is throughput: he said that many of MicroCal’s customers only needed to run one or two samples a day and would buy the VP-ITC, while end-users who needed to run dozens of samples a day would purchase the AutoITC. CSC manufactures the CSC ITC and the NanoITC III. The NanoITC III has greater sensitivity than the CSC ITC and allows for faster temperature adjustments, which lets users perform multiple runs at different temperatures without prolonged wait times. Sales of the CSC ITC are stronger in the materials market than in the biotech market, which is primarily served by the NanoITC III, according to Dr. Russell. Setaram distributes CSC’s ITC products in Europe. TA Instruments sells the TAM isothermal titration calorimetry (TAM-ITC) system. TA Instruments claims that the TAM-ITC can deliver faster response times by keeping its sample cell in an isothermic state. The company also offers “modular thermostats” that contain multiple microcalorimeters—up to 48 in the case of the TAM 48.

As is the case with most analytical techniques, with ITC there is a push for higher throughput and increased ease of use, but Dr. Brown also touched on the need for instruments that can obtain useful data from smaller sample sizes. Dr. Russell echoed this observation, couching it in terms of a call for greater sensitivity: “they call it sensitivity, but what they’re really wanting to do is say, ‘OK, instead of a half a milligram I want to give you two micrograms, and I want you to be able to do the same measurements on it.’ And so it’s simply using less material.” Another trend to expect in the development of ITC technology is the increased incorporation of probes in ITC systems, so that information about such characteristics as pH and oxygen tension can be obtained at the same time as thermodynamic information.

Future applications for ITC are likely to remain primarily in drug discovery and development, but Dr. Russell also hinted at a future possibility for the technology that lies outside its current markets: “one other area that is coming up—it’s starting to have a little bit of an impact but I think in the future it will have a more significant impact—as you look at biomaterials for other than the health industry, you’re starting to get into biomaterials for industrial products and that, I think, is going to be a

tremendous market.”

While ITC does not have a particularly large market size, IBO expects considerable sales growth for this technique in the future, given its utility in drug development and discovery, as well as the possibility of new applications opening up in the future.