It is well-known that during the formulation development of antibody and protein drugs, buffers help achieve the target pH value that is far from the isoelectric point (pI) of the drug (usually lower than the pI). Buffers possess strong buffering capacity, which can provide optimal physical and chemical stability for antibody protein molecules during processing, storage, and administration. Since the pI of most traditional monoclonal antibodies ranges from 5.9 to 9.0, a pH range of 4.5 to 6.5 is highly desired for monoclonal antibody formulations to balance the risks of physical and chemical degradation.

In addition, the pI of IgG4 typically ranges from 6 to 7.1; therefore, pH 5.0 is the ideal pH value for target formulations. This is because it can stabilize molecules by means of electrostatic repulsion and reducing the risk of deamidation at relatively high temperatures.

Although histidine dominates in both liquid and lyophilized products within the pH range of 5.5 to 6.5, there are still three other alternative buffers available if the target pH is between 4.5 and 5.5, namely acetate, citrate, and succinate. However, these buffering substances have certain inherent challenges that hinder their widespread use in intravenous and subcutaneous administration, as well as in liquid and lyophilized dosage forms. Histidine has a pKa value of 6 and exhibits poor buffering performance at pH < 5.5, thus its application is limited in the pH range of 4.5 to 5.5. Although acetate has good buffering capacity within this range, its volatility and excessive solvent loss during the freeze-drying process are potential challenges associated with its application. Citrate-buffered formulations have limited use in subcutaneous applications due to the risk of necrosis during subcutaneous injection. Succinate provides strong buffering capacity between pH 4.5 and 5.5, but its use in frozen or lyophilized applications is usually avoided. This is because succinate crystallization may affect product stability and lead to the risk of drastic pH fluctuations. The following table summarizes the limitations of using these four buffers in injectable formulations [1].

When comparing these buffer systems, succinate offers significant inherent advantages. First, with its pKa values of 4.2 and 5.6, succinate buffers provide excellent buffering capacity between pH 4.4 and 5.8. Second, unlike acetic acid, it is non-volatile, making it suitable for use in lyophilized products. Finally, succinate has been shown to have acceptable tolerability following in vivo administration. However, these advantages may be overshadowed by the risk that succinate tends to crystallize during freezing or lyophilization, which can cause pH fluctuations—and these fluctuations may compromise product stability.

Sundaramurthi et al. [2] emphasized the extent of pH changes in succinate caused by lyophilization in their work. In their study, succinate buffer solutions with concentrations ranging from 50 to 200 mM were cooled from 0°C to 25°C at a linear freezing rate of 0.5°C/min, and a low-temperature pH electrode was used to characterize the effect of freezing on pH. Their research showed that the magnitude and direction of pH fluctuations depend on the initial succinate concentration, initial solution pH, and freezing rate. Furthermore, these fluctuations can be mitigated by the presence of cosolutes such as proteins and sugars. Crystallization of succinate during freezing was identified as the root cause of its pH changes.

Anvay Ukidve et al. [1] evaluated the use of succinic acid as a buffer for monoclonal antibody formulations with pH between 4.5 and 5.5 in freezing, frozen storage, and lyophilization in their work. In their study, they found that 25 mM succinate could serve as a buffer for traditional monoclonal antibody formulations targeting pH 5.0; meanwhile, selective crystallization of monosodium succinate was identified as the root cause of pH changes. Additionally, their work confirmed that the crystallization of monosodium succinate could be reduced by adding 2% w/v sucrose, which significantly alleviated pH fluctuations. This enables succinate to be used in monoclonal antibody (mAb) drug formulations, and the formulations exhibited acceptable quality attributes in accelerated kinetic stability tests.

Adhering to its consistent commitment to high quality, Pfanstiehl has launched injectable-grade succinic acid (plant-derived) following the long-established sodium succinate (D-161). This new product features high purity, ultra-low endotoxins, and ultra-low metal residues. It undergoes individual testing for 29 types of metal ions, with additional quality 指標 (quality parameters) tested including DNA, RNA, DNase, RNase, lipase, and nitrite. It complies with the regulations of multiple pharmacopoeias (NF, EP, BP, JPE, ChP) and can be used in the production of biotherapeutic drugs and vaccines.

Product Information

· Product Name: Succinic Acid, High Purity, Low Endotoxin, Low Metals, NF, EP, BP, JPE, ChP (S-142)

· Chinese Name: 琥珀酸 (Hǔpò Suān, Succinic Acid)

· Molecular Formula: C?H?O?

· Molecular Weight: 118.09 g/mol

· CAS Number: 110-15-6

· Product Catalog No.: S-142

Product Features

· High purity, ultra-low endotoxins, ultra-low microbial content, and ultra-low residual metal impurities.

· Additional quality parameters tested: DNA, RNA, DNase, RNase, lipase, and nitrite.

· Complies with multiple pharmacopoeias: NF, EP, BP, JPE, ChP.

· Complies with ICH Q3D guidelines.

· Complies with GMP standards.

· US DMF and China CDE pharmaceutical excipient registration in progress.

Product Application

· Buffer

If you are interested in Pfanstiehl’s injectable-grade Succinic Acid (S-142), please contact Beijing XMJ Technology Co., Ltd., the authorized distributor of Pfanstiehl in China, to obtain the following detailed product overview documents and test samples.

[1]Anvay Ukidvea,1 , Kelvin B. Remberta,1,2 , Ragaleena Vanipentaa , Patrick Doriona,2 , Pierre Lafarguetteb , Timothy McCoya,2 , Atul Salujaa , Raj Suryanarayananc , Sanket Patkea, Succinate buffer in biologics Products；real world formulation considerations, processing risks and mitigation strategies. Pharmaceutics, Drug Delivery and Pharmaceutical Technology. 2022.

[2]Sundaramurthi P, Shalaev E, Suryanarayanan R. Calorimetric and diffractometric evidence for the sequential crystallization of buffer components and the consequential pH swing in frozen solutions. J Phys Chem B. 2010;114(14):4915–4923.

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