November 15, 2007 (Vol. 27, No. 20)
Lloyd Dunlap
Acoustic Dispensing at Forefront of New Techniques
Recently, the third IQPC “Compound Management & Integrity Conference” presented results of industry efforts to utilize innovations for the optimization of lead generation.
Jonathan C. O’Connell, Ph.D., associate director of lead discovery at Bristol-Myers Squibb (www.bms.com), led a workshop on the choice of integrating nanoliter acoustic compound-dispensing technology into a high-throughput screening environment.
The company uses an acoustic system rather than pin tools, which represent the only other technique available for dispensing volumes in the low nL range, according to Dr. O’Connell. Among the critical decisions that must be made with regard to choosing between these technologies, he explained, are picking the best strategy—just-in-time or predispensed compounds; timing of assays and how dispensing strategy influences this; and managing the process of storage, evaporation, water uptake, and distribution through hit identification, lead evaluation, and high-throughput ADMET assays.
Dr. O’Connell also discussed the use of chemiluminescence nitrogen detection (CLND) for the absolute measurement of compound concentrations. He noted that CLND has been around for some time but has the reputation of being complicated, which may be undeserved. The technique, which measures compound concentration as opposed to purity, has been embraced by biotech companies more so than pharmas. When asked why, Dr. O’Connell admitted that he had no answer but thinks CLND is an interesting space to keep an eye on.
Dr. O’Connell examined the cost-benefit ratio of using the acoustic system. He noted that the acoustic technology pays for itself due to the noncontact nature of the liquid transfer, which eliminates problems associated with carryover and avoids elaborate washing procedures that significantly increase solvent consumption. Pin tools use surface tension to dip in, pick up a drop, and make the transfer, which means they have to be vigorously washed between transfers.
Bristol-Myers Squibb has integrated the acoustic dispensing technique into its HTS function rather than compound management, making the transfer just in time onto assay plates, Dr. O’Connell reported.
“With such small volumes, typically between 25 and 50 nL, what you put on a plate doesn’t stay around long,” he observed. “When will the assay procedure be adding reagents? Will your compound have dried down? There’s no point in having the best possible assay if the compound doesn’t come back up into solution.”
It’s obvious that the industry has embraced acoustic technology. What is less apparent, Dr. O’Connell said, is how to take care of compounds as they move through the screening process. “There are divergent views on this issue, in terms of storage temperature, water-uptake limits, and freeze-thaw cycles.”
ASDI BioSciences (www.asdibiosciences.com) has at least some of the answers, according to Rick Hammar, director of compound management, chemistry, screening services. Established in 1988, ASDI’s core business was initially the sale of screening compounds originating within the former Soviet Union. Now the company’s mission is distributing ready-to-use screening compounds as well as providing repository storage as alternatives to compound management.
To accomplish this, Hammar stated that sample preparation is a key skill set. “ASDI does everything a compound management group does” to speed up throughput, decrease costs, and heighten sample integrity.
The move to custom-made benchtop enclosures in which all liquid handling is done with automated liquid-handling vortexers and mixers is one technique that has been implemented. Dimethyl sulfoxide is a great solvent but exhibits a strong affinity for moisture, Hammar explained. To counter this, stock solution creation is done in the enclosures under argon and nitrogen, which increases the shelf life of almost all research collections. ASDI also offers inert atmospheres for solids but generally only for building blocks on the synthesis side.
Another important difference in ASDI’s approach, Hammar pointed out, is related to infrastructure and demand. “Resources can be stretched by demand in terms of space, equipment, and head count, sometimes for a one-off project. So, ASDI’s staff is cross-trained to achieve optimal adaptability to the cyclic nature of business demand. Clients can avoid both one-time and long-term costs by outsourcing their full material collection services.”
U.S. pharma has traditionally been reluctant to allow its chemical collections to go overseas, at least without the kind of safeguards ASDI has in place, Hammar noted. Before it calls upon its Ukraine or Thailand laboratories, chemistry analysis and sample preparation are done in Delaware and approved by the client. The company’s offshore labs maintain U.S. methods and are under U.S.-based management.
“Accuracy, efficiency, and experience are our drivers,” Hammar said. “Typically, we deliver in 24 hours any collection we’re holding, from one sample up to 2,000.” Hammar also noted that there is a trend among big pharma to move toward a centralized collection. Academics as well are pooling into single repositories and distribution centers with the capability of distributing in any format, container type, and form, from dry to preplated sets.
“The goal is increased productivity, decreased costs, and enhanced sample quality and, ultimately, an accelerated rate of drug development, from hit to lead to candidate,” Hammar summarized.
Suresh Poda, Ph.D., scientist-II, HTS, with Lundbeck Research USA (www.lundbeck.com) described his company’s new automated liquid compound management system, ALiCoM. It is a ministore with an integrated Tecan RSP100 and Echo 550 that has the capacity to store 1.6 million compounds in 384-well microplates at
-20ºC. The plates are ready for HTS with cherry picking capability, from the same or different collections.
Lundbeck needed an automated system to handle a significant increase in its compound collection, HTS targets, and screens per year. MatriCal (www.matrical.com) was contacted to provide the ministore.
The resulting system has a 1.6 million compound capacity, which Dr. Poda calculates should meet Lundbeck’s requirements for the next five years without requiring expansion. The ministore accommodates a variety of sample types and formats such as microplates as well as 96 and 384 minitubes and can be customized to store multiple media types.
The Echo 550 is used for liquid volumes from 2.5 to 1,000 nL, with the Tecan coming into play for volumes larger than 1 µL for dose-response studies and handling tubes. Acoustic transfer is used as the main driver for compound transfer, Dr. Poda said. It results in lower CVs at less volumes; fast cherry picking—40 samples/plate in less than one minute up to 250 nL; and lower operational cost, he added.
Lundbeck selected ASDI Biosciences for compound preparation and long-term storage. “They are prepared to weigh approximately 500 compounds per day at peak efficiency and work with DMSO under dry conditions,” Dr. Poda told the conference. ASDI will also store multiple copies of the collection at -20ºC under controlled humidity.
ChemDiv (www.chemdiv.com), another organization of Russian origin presenting at IQPC, remains heavily involved in the drug discovery process in that country through its affiliate, Chemical Diversity Research Institute (CDRI). President and CEO, Nikolay Savchuk, Ph.D., described how his company is contributing to the evolution of “the drug discovery roadmap by doing drug discovery everywhere.” ChemDiv merges industrial and academic efforts to bring new approaches to the treatment of life-threatening diseases, according to Dr. Savchuk.
It now has more than one million small molecules in its library, which grows by about 20% every year. The company has 500 scientists at its two locations in Moscow and San Diego.
On the meta-roadmap that Dr. Savchuk evoked, medicinal chemistry is a key tool for obtaining small molecule leads and molecular probes. As part of the process, ChemDiv is partnering with national roadmaps and screening center initiatives. As a service research organization (SRO), ChemDiv collaborates with pharma, academic institutions, and NGO discovery initiatives that span the spectrum of international institutions, Dr. Savchuk pointed out. “What we see across all these initiatives is medicinal chemistry as an enabling technology,” Dr. Savchuk states.
Assay-ready Compound Plates
Merck Frosst’s (www.merckfrosst.ca) Montreal-based facility is saving the equivalent of three biologists per year with its new system for delivering assay-ready compound plates for drug screening, reported Louis-Jacques Fortin, compound manager.
Just 10 years ago, vials were distributed to biologists for screening. They were stored in different locations under different conditions and when misplaced, required a new solution to be made with resulting waste of time and materials.
The objectives of the new system was to increase efficiency and productivity with a centralized compound management system and provide biologists assay-ready compound plates for screening.
To achieve this end, Merck Frosst implemented an automated sample store and cold room (RTS Life Sciences), storage labware, its ordering software MAPS, and its Plating software with an integrated Tecan Liquid Handler. All labware is stored on fiberglass trays. The room can handle a flexible array of sample allocations like 17,500 deep plates, 7,800 shallow plates, and 48,000 minitubes. Converted to all minitubes, storage area capacity is more than one million.
To protect samples from excessive exposure to light, the room’s lights go on only when the robot moves to transport trays from storage to the picking station. Here a second robot picks the designated minitubes, places them in transport racks, and moves the racks to a conveyor that supply stackers where the compounds are thawed and ready to be plated. The unit can pick about 384 tubes per hour, Fortin noted.
The polypropylene minitubes, supplied by Abgene (www.abgene.com), feature a pierceable septum that minimizes exposure to the environment. “In a 21-week period,” Fortin said, “there was only a 0.47% change in DMSO mass.”
The MAPS software allows users to choose compounds and plates with the click of a mouse. The system automatically reserves minitubes with the highest volume and clicking on the column header sorts them by concentration. The user also selects plate format and chooses the diluent. The Plating software reads the worklist provided by MAPS and sends commands to the Tecan to aspirate and dispense controls and compounds as well as instructions for plate format, and liquid classes, as well as diluent, mixing, and washing routines.
In addition to the manpower savings Fortin cited, the system minimizes compound waste, helps ensure the integrity of compounds through improved storage conditions, provides additional security by restricting compounds to specific research groups when desirable, and improves assay performance due to serial dilutions being performed by the same liquid handlers.
