Needle clogging of protein solutions in prefilled syringes: A two-stage process with various determinants

Does needle clogging change the spatial distribution of injected drug in tissue? New insights by X-ray computed tomography

Prefilled syringes (PFS) are primary packaging materials that offer convenience and safety for subcutaneous injection of parenteral drug solutions. However, an increasingly common problem with the trend towards higher drug concentrations is the clogging of the needle during storage due to evaporative water loss and consequent solidification of the drug. In contrast to all previous studies on this topic, this work focuses on pharmacokinetically relevant aspects and investigates the effects of needle clogging on the spatial distribution of the injected drug in the tissue. X-ray computed tomography (XCT) (both tube-based and synchrotron-based) was used to visualize and analyze the spreading pattern and the fate of the injected liquid in porcine skin. By using controlled injection and force measurement the tissue distribution was correlated with the plunger force profile and the fluid dynamics of the jet. Studies of monoclonal antibody solution demonstrate that clogs, which are formed by evaporation of water and solidification of drug solution in the needle tip, usually dissolve in the flow of the liquid during injection. In the initial injection phase, the liquid jet starts to escape the needle only through a narrow channel in the clog. The resulting high dynamic pressure can alter the distribution of the liquid in the tissue, causing a long tail of liquid that penetrates deep into the fibrous network of the subcutaneous layer. However, the volume of this tail was calculated to be low relative to the overall volume of the injected drug solution (less than 2.4%) and is therefore unlikely to have a significant effect on the absorption kinetics of the injected drug. In addition, it was shown that if a clog were to enter the tissue, it would quickly dissolve.

Injectability of high concentrated suspensions using model microparticles

Administration of high-concentrated suspension formulations (i.e., solid particles dispersed in a liquid vehicle) can be limited due to their greater propensity for needle occlusion. The physical interaction between the solid phase (i.e., particles), the vehicle (i.e., flow field), and injection devices could result in the formation of particle bridging or filtering, posing a major risk in dose delivery accuracy and injectability. Here, given the limited understanding on how clogging initiates in syringe and needle delivery systems, we report an experimental approach to fully characterize the transient injection behavior of suspensions. In particular, we first established a custom fluorescence tagging and imaging technique with integrated force sensor to enable visual observation of local particle concentrations and plunger force monitoring throughout injection. Then, we investigated the effects of key formulation properties and device parameters including particle concentration and morphology, carrier viscosity, injection rate, needle and syringe sizes, and tissue backpressure on the incidence of suspension particle jamming and needle clogging. We performed systematic benchmark studies demonstrating that increasing needle inner diameter (ID) and particle density considerably reduced clogging risk, while increasing vehicle viscosity, particle size, and tissue backpressure significantly increased clogging. The experimental framework presented is amenable to quantifying clogging risk in drug-loaded particle suspensions and provides a guideline to make informed decisions on the tradeoffs between creating particles for pharmaceutical impact and feasibility of injection delivery.

Towards a better understanding of light-glucose induced modifications on the structure and biological activity of formulated Nivolumab

In the last years, monoclonal antibodies (mAbs) have rapidly escalated as biopharmaceuticals into cancer treatments, mainly for their target specificity accompanied by less side effects than the traditional chemotherapy, and stimulation of reliable long-term anti-tumoral responses. They are potentially unstable macromolecules under shaking, temperature fluctuations, humidity, and indoor and outdoor light exposure, all stressors occurring throughout their production, transport, storage, handling, and administration steps. The chemical and physical modifications of mAbs can lead not only to the loss of their bioactivity, but also to the enhancement of their immunogenicity with increasing risk of severe hypersensitivity reactions in treated patients because of aggregation. The photostability of Nivolumab, the active principle of Opdivo®, has been here studied. The chemical modifications detected by LC-MS/MS after the light stressor showed Trp and Met mono and double oxidations as primary damage induced by light on this mAb. The oxidations were stronger when the mAb was diluted in sterile glucose solution where 5-HMF, a major heat glucose degradation product, acted as singlet oxygen producer under irradiation. However, no significant changes in the mAb conformation were found. On the contrary, formation of a significant extent of aggregates has been detected after shining high simulated sunlight doses. This again took place particularly when Nivolumab was diluted in sterile glucose, thus raising a direct correlation between the aggregation and the oxidative processes. Finally, the biological activity under light stress assessed by a blockade assay test demonstrated the maintenance of the PD-1 target recognition even under high light doses and in glucose solution, in line with the preservation of the secondary and tertiary structures of the mAb. Based on our results, as sterile glucose is mostly used for children's therapies, special warnings, and precautions for healthcare professionals should be included for their use to the pediatric population.

Unraveling Pre-filled Syringe Needle Clogging: Exploring a Fresh Outlook Through Innovative Techniques

OBJECTIVE

This study aimed to investigate the movement of liquid in the needle region of staked-in-needle pre-filled syringes using neutron imaging and synchrotron X-ray tomography. The objective was to gain insights into the dynamics of liquid presence and understand the factors contributing to needle clogging.

METHODS

Staked-in-needle pre-filled syringes were examined using neutron radiography and synchrotron X-ray phase-contrast computed tomography. Neutron radiography provided a 2D visualization of liquid presence in the needle, while synchrotron X-ray tomography offered high-resolution 3D imaging to study detailed morphological features of the liquid.

RESULTS

Neutron radiography revealed liquid presence in the needle region for as-received samples and after temperature and pressure cycling. Pressure cycling had a more pronounced effect on liquid formation. Synchrotron X-ray tomography confirmed the presence of liquid and revealed various morphologies, including droplets of different sizes, liquid segments blocking sections of the needle, and a thin layer covering the needle wall. Liquid presence was also observed between the steel needle and the glass barrel.

CONCLUSIONS

The combination of neutron imaging and synchrotron X-ray tomography provided valuable insights into the dynamics of liquid movement in staked-in-needle pre-filled syringes. Temperature and pressure cycling were found to contribute to additional liquid formation, with pressure changes playing a significant role. The detailed morphological analysis enhanced the understanding of microstructural arrangements within the needle. This research contributes to addressing the issue of needle clogging and can guide the development of strategies to improve pre-filled syringe performance.

Viscosity increase/gelation of therapeutic IgG monoclonal antibodies induced by Zn2+: one possible root cause of clogging of staked-in-needle prefilled syringes

We investigated the elution of zinc ions (Zn²⁺) from the elastomer of rigid needle shields (RNS) attached to staked-in-needle prefilled syringes (SIN-PFS) and the physicochemical impacts of Zn²⁺ on therapeutic IgG monoclonal antibody (mAb) solutions. The elution of metal ions from typical RNS elastomer under realistic buffer and storage conditions was investigated by inductively coupled plasma-mass spectrometry. Among the metal ions examined, only Zn²⁺ was detected. The elution of Zn²⁺ from RNS elastomer was found to be buffer-dependent. We investigated the influence of Zn²⁺ on the viscosity of seven mAb solutions at 180 mg/mL. The effect of Zn²⁺ clearly depended on antibody type. Drastic increases in viscosity or gelation were observed in four out of the seven mAbs. Dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) showed the effect of Zn²⁺ on mAb viscosity was explained by the colloidal destabilization of mAb solutions. Thus, Zn²⁺ leaching from RNS elastomer may possibly increase viscosity or cause gelation, and consequently cause possible needle clogging during long-term storage. DLS and SAXS can predict reactivity of mAbs to Zn²⁺, and require only small amounts of samples. This makes it possible to predict compatibility with RNS elastomer and evaluate needle clogging risk in SIN-PFSs in the early stages of mAb development.