Long-Acting Implant Injection Deserves a Place in Drug Development Strategy

What Implant Injection Actually Is and Why the Physics Works in Its Favour

The Gaplast implant syringe. After the implant rod is advanced into the subcutaneous channel, the cannula withdraws automatically into the syringe body and is concealed by the needle shield.

A drug-loaded implant rod is a polymer matrix — either biocompatible but non-degrading, or fully biodegradable — into which an active pharmaceutical ingredient has been mixed before extrusion. The resulting rod is small: diameters typically run from 0.1 mm to 3 mm, lengths from 3 mm to 40 mm. Once placed subcutaneously, the drug diffuses out of the polymer matrix at a controlled rate over weeks, months or years depending on the formulation and the polymer grade chosen.

The pharmacokinetic advantage is significant. Conventional injections, whether intravenous or subcutaneous bolus, produce concentration peaks that can push transiently into toxic or ineffective ranges depending on the molecule and the indication. A sustained-release implant removes those peaks entirely, maintaining drug concentration within the therapeutic window for the duration of the dosing period. For potent APIs — including oncology agents — this controlled delivery profile is not simply a convenience. It is a meaningful safety and efficacy argument.

The current approved implant market skews toward small molecules, which account for 64% of drug substances, with biologics comprising the remaining 36%. The principal constraint on molecule selection is thermal stability during extrusion and the required drug-to-polymer loading ratio. These are formulation challenges that require pharmaceutical development expertise, but they are not categorical barriers. The approved product list spans women’s health, oncology and ophthalmology as the three largest therapy areas, with hormone therapy, anti-ageing and biotech applications also represented.

The Gaplast syringe is available in two standard configurations designated 1M and 3M, corresponding to cannula outer diameters of 1.6 mm and 2.1 mm respectively. The device is designed for a 45-degree injection angle that ensures placement in subcutaneous tissue rather than muscle. Its distinguishing mechanical feature is automatic cannula withdrawal: after the plunger advances the implant rod into the subcutaneous channel, the cannula retracts into the syringe body and is concealed behind the needle shield. This means the implant is deposited in the access channel rather than driven deeper into undisturbed tissue, and the needle is never exposed during or after removal.

Ingmar Kneer, Product Manager Drug Device Systems, Gaplast. Kneer has supported implant syringe development, production and sales since 2008.

The Compliance and Sustainability Arguments for Long-Acting Administration

The case for long-acting implants extends beyond pharmacokinetics. In any therapy requiring regular medication over months or years — cardiovascular disease, diabetes, inflammatory conditions, hormone-dependent oncology — the principal risk outside of the clinical encounter is non-compliance. A patient who receives a drug-loaded implant administered by a healthcare professional at a scheduled visit has their dosing assured for the entire intended period. There is no daily decision to make, no missed dose, no cumulative underdosing and no re-exposure to administration risk at each interval.

The sustainability dimension is also substantial. A three-month treatment course delivered by daily pre-filled syringe generates 90 syringes, 90 packaging units and 90 individual administration events, each carrying its own adverse event risk. A weekly regimen still produces 12 of each. The equivalent drug-loaded implant involves a single device, a single administration and a single packaging unit. For programmes where the implant uses a biodegradable polymer matrix, there is no requirement for a second clinical procedure to remove the implant at the end of the dosing period — it resorbs in situ. This is the distinction Kneer highlights as potentially transformative for contraception applications: a one-year biodegradable contraceptive implant placed during a routine examination, with no removal required, addresses the second clinical visit as a barrier to uptake.

Where the Market Is Going and What Is Still Untapped

The global implant drug market is projected to grow from approximately $4 billion to $4.7 billion over the next five years, at a compound annual growth rate of 4.2%. That is slightly below the healthcare sector average, which reflects the maturity of established therapy areas rather than a ceiling on the technology. In oncology specifically, the primary tract substances goserelin and leuprorelin are forecast to grow at 6% to 7% annually, driven by the continuing prevalence of hormone-sensitive cancers and the clinical preference for controlled long-term androgen suppression.

The more significant signal is the increase in generic approvals. Prior to 2018, the approval pipeline was dominated by originator products. Since then, generic and originator products have been approved at roughly equal rates. This means pharmaceutical companies with existing development capability in the implant space can enter established commercial markets. It also means that the device supplier must be capable of supporting the full quality and regulatory infrastructure that generic development requires — GMP cleanroom production, bioburden testing, certificates of conformance and analysis, and validated sterilisation processes. Gaplast supports gamma, ETO and e-beam sterilisation, with autoclaving excluded due to material constraints.

The unexplored territory is larger. Cardiovascular disease, generalised inflammatory disease and diabetes are the three most compelling candidates for implant administration among long-term therapy areas not currently served by the technology. In each case, the argument is the same: consistent drug exposure over extended periods is both therapeutically preferable and practically achievable through subcutaneous implant, and the compliance advantage over daily or weekly oral or injectable regimens is material. Veterinary medicine is a further application area, noted as an emerging opportunity where the demand characteristics map closely to those of human long-acting injectable programmes.

Gaplast is a family-owned company established in 1989 and headquartered in Bavaria, Germany. Its implant syringe programme began in 2008 and the company’s product range covers container closure systems, airless bag and bottle systems and drug delivery systems. Syringe manufacture follows a cleanroom injection moulding, assembly and quality control process, with the device delivered to pharmaceutical companies in two subassemblies — syringe body and plunger — for filling and final assembly at the fill-finish site.