Researchers headed by a team at New York University (NYU) College of Dentistry’s Pain Research Center have identified a compound, designated CBD3063, that in animal studies reversed four types of chronic pain.
The small molecule—one of 27 million screened in a library of potential new drugs—binds to an inner region of a calcium channel to indirectly regulate it. Tests in rats and mice showed the molecule outperformed gabapentin (GBP) without troublesome side effects, providing a promising candidate for treating pain. “Identifying this first-in-class small molecule has been the culmination of more than 15 years of research,” said research lead Rajesh Khanna, PhD, director of the NYU Pain Research Center and professor of molecular pathobiology at NYU Dentistry. “Though our research journey continues, we aspire to present a superior successor to gabapentin for the effective management of chronic pain.”
Khanna and colleagues reported on their findings in PNAS, in a paper titled “A peptidomimetic modulator of the CaV2.2 N-type calcium channel for chronic pain,” in which they concluded, “In short, CBD3063 may be a superior successor in pain management.”
Calcium channels play a central role in pain signaling, in part through the release of neurotransmitters such as glutamate and GABA—“the currency of the pain signal,” according to Khanna. The transmembrane Cav2.2 (or N-type) transmembrane voltage-gated calcium channel plays a central role in pain, by providing the Ca2+ for sustained neuronal firing and neurotransmitter release, the team further explained.
This calcium channel is the target for three clinically available drugs, including ziconotide, and gabapentin and pregabalin, which are widely used to treat nerve pain and epilepsy.
Gabapentin mitigates pain by binding to the outside of the Cav2.2 calcium channel, affecting the channel’s activity. However, the authors noted, “Both gabapentinoids have low efficacy and present with serious side effects.” Yet, as they pointed out, these gabapentinoids remain first-line neuropathic pain treatments. “Developing effective pain management with minimal side effects is crucial.”
Developing new therapies has been challenging. Khanna has long been interested in a protein called collapsing response mediator protein 2 (CRMP2), a key regulator of the Cav2.2 calcium channel that binds to the channel from the inside. “Rather than directly going after known targets for pain relief, our lab is focused on indirectly targeting proteins that are involved in pain,” Khanna noted.
Khanna and colleagues had previously discovered a peptide derived from CRMP2 that could uncouple CRMP2 from the calcium channel. When this peptide—dubbed the calcium channel‐binding domain 3; CBD3—was delivered to cells, it acted as a decoy, blocking CRMP2 from binding to the inside of the calcium channel. This resulted in less calcium entering the calcium channel and less neurotransmitter release, which translated to less pain in animal studies. The authors explained, “We identified an intrinsically disordered 15-amino-acid peptide (designated CBD3, for calcium channel binding domain 3) from CRMP2 that interferes with the Cav2.2–CRMP2 interaction and decreases calcium influx, transmitter release, and acute, inflammatory, and neuropathic pain.”
However, peptides are difficult to synthesize as drugs because they are short-acting and easily degrade in the stomach, so the researchers sought to create a small molecule drug based on CBD3. Starting with the 15 amino acids that make up the CBD3 peptide, they had honed in on two amino acids that studies showed were responsible for inhibiting calcium influx and mitigating pain. “Subsequent work identified the first six amino acids ARSRLA as the core peptide with two residues (Ala1 and Arg4) critical for binding affinity,” they wrote. “At that point, we realized that these two amino acids could be the building blocks for designing a small molecule,” said Khanna.
In collaboration with colleagues at the University of Pittsburgh, the researchers ran a computer simulation that screened a library of 27 million compounds to look for a small molecule that would “match” the CBD3 amino acids. The simulation narrowed the library down to 77 compounds, which the researchers experimentally tested to see if they lessened the amount of calcium influx. This further pared the pool down to nine compounds, which were assessed using electrophysiology to measure decreases in electrical currents through the calcium channels.
One compound, CBD3063, emerged as the most promising candidate for treating pain. Biochemical tests revealed that CBD3063 disrupted the interaction between the CaV2.2 calcium channel and CRMP2 protein, reduced calcium entering the channel, and lessened the release of neurotransmitters.
“Many scientists have screened the same library of compounds, but have been trying to block the calcium channel from the outside,” Khanna pointed out. “Our target, these two amino acids from CRMP2, is on the inside of the cell, and this indirect approach may be the key to our success.”
Khanna’s lab tested CBD3063 with mouse models for pain related to injury. The compound was effective in alleviating pain in both male and female mice—and notably, in a head-to-head test with the drug gabapentin, the researchers needed to use far less CBD3063 (1-10 mg) than gabapentin (30 mg) to reduce pain.
To explore whether CBD3063 helped with different types of chronic pain, Khanna partnered with researchers at Virginia Commonwealth University, Michigan State University, and Rutgers University. Collaborators ran similar studies administering CBD3063 to treat animal models of chemotherapy-induced neuropathy, inflammatory pain, and trigeminal nerve pain, and all successfully reversed pain, similar to the effects of gabapentin But unlike gabapentin, the use of CBD3063 did not come with side effects such as changes to heart rate and breathing, sedation, or changes to cognition such as memory and learning.. “Notably, CBD3063, via four different routes of administration, reversed nociceptive behaviors in four distinct pain models across two different species and both sexes,” they stated. “Importantly, this occurred without altering sensory, sedative, affective, or cognitive behaviors … CBD3063 is a selective, first-in-class, CRMP2-based peptidomimetic small molecule, which allosterically regulates Cav2.2 to achieve analgesia and pain relief without negative side effect profiles.
“The researchers are continuing to study CBD3063, refining its chemical composition and running additional tests to study the compound’s safety and assess if tolerance develops. “In upcoming research, enhancements aimed at optimizing the central nervous system exposure and the absorption, distribution, metabolism, and excretion characteristics of CBD3063 will be undertaken,” they commented. Long term, they hope to bring a CBD3063-derived drug to clinical trials in an effort to offer new options for safe and effective pain relief. “In summary, CBD3063 could potentially be a more effective alternative to GBP for pain relief.”