Needle-free administration of enfuvirtide reduces injection site reactions

A small eight-week study of a needle-free injection device for enfuvirtide (T-20, Fuzeon) sponsored by the drug's manufacturers, Roche and Trimeris, has shown the device to be as effective as injection by needle, without causing as much pain, discomfort and swelling.

The fusion inhibitor enfuvirtide is composed of a very large drug molecule. It cannot be taken orally, since the digestive system would break the drug down into smaller molecules that would not be effective against HIV. Until now, enfuvirtide has been taken by twice-daily subcutaneous injections that very frequently cause painful swellings and other unpleasant “injection site reactions” (ISRs).

The drug is prepared in the same way no matter which injection method is used – a prepared powder is dissolved in sterile water to produce an injectable liquid. When 27-gauge needles are used to inject the liquid subcutaneously (below the skin), the entire dose forms a ‘bubble’ below the skin surface. This tends to produce hard nodules at the injection site which can be painful, and prevents the site from being used again until the nodule has cleared.

Instead of needles, a hand-held needle-free injection device (NFID) called the ‘Biojector B2000’ can also be used to administer enfuvirtide. The B2000 uses pressurised gas to ‘blast’ the liquid below the skin surface. This avoids the need for needle punctures, and disperses the drug more evenly over a larger area. While the B2000 has been in use for some time, it has not been well-studied in randomised clinical trials. However, a community pharmacy who provided the B2000 to 726 individuals reported promising results at the recent Sixteenth International AIDS Conference in Toronto.

The study used a ‘crossover’ methodology to compare both injection methods for participants who were beginning enfuvirtide for the first time. Participants were randomized to begin with either the Biojector B2000, or standard 27-gauge needles. After four weeks, they switched over to the opposite method. All participants who completed the study had therefore tried both methods, and were able to compare their satisfaction levels, preference, and adherence. Minimum blood concentration levels were also monitored to ensure that effective enfuvirtide doses were being delivered.

Fifty-eight people were enrolled – about half of whom were Caucasian and 85% of whom were white, an average of 43 years old, with a median of 203 CD4 cells/mm³ and 4.6 log viral load. (Fifty-four percent had previous experience with self-injection.) Of these, 49 went on to actually start taking enfuvirtide, data on at least one dose was available for 48, and 39 completed the full 8-week study.

Drug concentration levels were similar for both methods, especially when non-adherent patients were left out of the comparison. The average minimum concentration of enfuvirtide achieved by Biojector was 2,038 ng/mL, and 2,204 ng/mL by subcutaneous needles.

Although almost all participants had some degree of ISR no matter which method was used, the reactions were considerably less severe with the Biojector B2000. Participants overwhelmingly (84%) rated the Biojector as the preferable method. The researchers concluded that “[needle-free injection device] administration of [enfuvirtide] resulted in a substantially lower incidence of painful nodules… was preferred by most patients over standard [27-gauge needles], and is generally safe and well-tolerated.”