A clinical case of the use of a new selective μ1-opioid analgesic Tafalgin in the treatment of chronic cancer pain

In the Russian Federation, tetrapeptide tyrosyl-D-arginyl-phenylalanyl-glycine amide (Tafalgin), a novel analgesic, selective agonist of μ1-opioid receptors, was developed and approved in 2022. The article presents the first experience of the successful use of Tafalgin in treating chronic pain in a cancer patient with poor tolerance to traditional opioids (tramadol, tapentadol, morphine). At baseline, pain severity, according to the Neurological Rating Scale (NRS), was 5–7 points at rest and up to 9 points in motion out of the maximum 10. The combination of 400 mg/day of tramadol with gabapentin and a non-steroidal anti-inflammatory drug was ineffective; 400 mg/day of tapentadol in combination with gabapentin and a non-steroidal anti-inflammatory drug also was ineffective. Morphine tablets 60 mg/day were effective (NRS score of 2–3), but unrelenting nausea and vomiting were unmanageable and significantly reduced quality of life. Reducing the dose of oral morphine to 20 mg/day mitigated adverse events but reduced the effectiveness of pain relief (resting NRS score of 4 points). Tafalgin 4 mg subcutaneously BID, then TID reduced the pain severity to an average daily NRS score of 1.22 over the first 3 days of treatment with no adverse events. Sleep, appetite, and physical activity improved. The patient received Tafalgin for 84 days, and she gained 5 kg due to improved nutrition during that time. The drug is comparable in efficacy to morphine and is associated with fewer adverse events. A limitation to widespread use is the availability of a formulation for subcutaneous injection only.