Targeted chemotherapy with nanoparticle albumin-bound paclitaxel (nab-paclitaxel) in metastatic breast cancer: which benefit for which patients?

HSADab: A comprehensive database for human serum albumin

Human Serum Albumin (HSA), the most abundant protein in human body fluids, plays a crucial role in the transportation, absorption, metabolism, distribution, and excretion of drugs, significantly influencing their therapeutic efficacy. Despite the importance of HSA as a drug target, the available data on its interactions with external agents, such as drug-like molecules and antibodies, are limited, posing challenges for molecular modeling investigations and the development of empirical scoring functions or machine learning predictors for this target. Furthermore, the reported entries in existing databases often contain major inconsistencies due to varied experiments and conditions, raising concerns about data quality. To address these issues, a pioneering database, HSADab, was established through an extensive review of >30,000 scientific publications published between 1987 and 2023. The database encompasses over 5000 affinity data points at multiple temperatures and >130 crystal structures, including both ligand-bound and apo forms. The current HSADab resource (www.hsadab.cn) serves as a reliable foundation for validating molecular simulation protocols, such as traditional virtual screening workflows using docking, end-point, and al-chemical free energy techniques. Additionally, it provides a valuable data source for the implementation of machine learning predictors, including plasma protein binding models and plasma protein-based drug design models.

The interplay of solvent-drug-protein interactions during albumin nanoparticles formulations for temozolomide delivery to brain cancer cells

OBJECTIVES

Temozolomide (TMZ), the first line for glioma therapy, suffers from stability at physiological pH. TMZ was selected as a challenging model drug for loading into human serum albumin nanoparticles (HSA NPs). Our aim is to optimise the conditions for TMZ loading into HSA NPs while ensuring TMZ stability.

METHODS

Blank and TMZ-HSA NPs were fabricated using the de-solvation technique and the effect of different formulation parameters was evaluated.

KEY FINDINGS

For blank NPs, crosslinking time had no significant effect on NPs' size while acetone produced significantly smaller particles than ethanol. Upon drug loading, though TMZ was stable in acetone and ethanol as single agents yet, ethanol-based NPs showed misleadingly high EE% due to drug instability in ethanol formulations as evident by the UV spectrum.The optimum conditions for drug-loaded particles were: 10 mg/ml HSA, 4 mg TMZ using acetone, yielded NPs with 145 nm in diameter, ξ of -16.98 mV and 0.16% DL. The selected formula reduced the cell viabilities of GL261 glioblastoma cells and BL6 glioblastoma stem cells to 61.9% and 38.3%, respectively.

CONCLUSIONS

Our results corroborated that careful manipulation of TMZ formulation processing parameters is crucial for encapsulating such chemically unstable dug while simultaneously ensuring its chemical stability.

Toxicity of Nab-Paclitaxel Compared to Paclitaxel in a Tertiary Hospital in Jeddah, Saudi Arabia: A Retrospective Cohort Study

Background Nanoparticle albumin-bound paclitaxel has been developed to avoid the toxicities associated with Cremophor-solved paclitaxel. Although many studies confirm this hypothesis, there is recent evidence showing no difference between paclitaxel and nab-paclitaxel in their efficacy and safety profile. This study further assesses the toxicity of both paclitaxel and nab-paclitaxel in adult patients with breast and pancreatic cancer in a tertiary hospital in Jeddah, Saudi Arabia. These toxicities include neutropenia, anaemia, and effects on kidney and liver functions. Methods The study is a retrospective cohort study done at King Abdulaziz University Hospital, Jeddah, Saudi Arabia, from January 2018 to December 2021, conducted on patients diagnosed with breast or pancreatic cancer treated with paclitaxel or nab-paclitaxel. Results There is a statistically significant difference between the two groups in developing anaemia, renal, and liver toxicity (P<0.05). On the other hand, there are no statistically significant differences in developing neutropenia between the two groups (P=0.084). Conclusions Nab-paclitaxel might not be better than paclitaxel in reducing the risk of neutropenia, anaemia, and liver toxicity, as predicted. Nevertheless, both medications require that the patient's renal functions be monitored during the treatment. Further studies conducted in multiple oncology centres with a larger sample are needed to evaluate the toxicity of paclitaxel and nab-paclitaxel in adult patients with breast and pancreatic cancer.

Novel Development of Nanoparticles-A Promising Direction for Precise Tumor Management

Although the clinical application of nanoparticles is still limited by biological barriers and distribution, with the deepening of our understanding of nanoparticles over the past decades, people are gradually breaking through the previous limitations in the diagnosis and treatment of tumors, providing novel strategies for clinical decision makers. The transition of nanoparticles from passive targeting to active tumor-targeting by abundant surface-modified nanoparticles is also a development process of precision cancer treatment. Different particles can be used as targeted delivery tools of antitumor drugs. The mechanism of gold nanoparticles inducing apoptosis and cycle arrest of tumor cells has been discovered. Moreover, the unique photothermal effect of gold nanoparticles may be widely used in tumor therapy in the future, with less side effects on surrounding tissues. Lipid-based nanoparticles are expected to overcome the blood-brain barrier due to their special characteristics, while polymer-based nanoparticles show better biocompatibility and lower toxicity. In this paper, we discuss the development of nanoparticles in tumor therapy and the challenges that need to be addressed.

Nab-paclitaxel plus S-1 versus oxaliplatin plus S-1 as first-line treatment in advanced gastric cancer: results of a multicenter, randomized, phase III trial (GAPSO study)

Background:

This study aimed to investigate the superiority of nab-paclitaxel plus S-1 (AS) over oxaliplatin plus S-1 (SOX) in patients with advanced gastric cancer (AGC).

Methods:

In this multicenter, randomized, phase III superiority trial, eligible patients with unresectable, locally advanced gastric adenocarcinoma were recruited and randomly assigned (1:1) to receive AS (nab-paclitaxel 260 mg/m² on day 1 or 130 mg/m² on days 1 and 8; oral S-1 40–60 mg twice daily for 14 days) or SOX (130 mg/m² oxaliplatin on day 1; oral S-1 40–60 mg twice daily for 14 days) every 3 weeks for up to six cycles. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were overall survival, objective response rate, and safety.

Results:

Owing to slow enrolment, an unplanned interim analysis was performed, resulting in the early termination of the study on 31 December 2021 (data cutoff). Between March 2019 and March 2021, 97 patients (AS, n = 48; SOX, n = 49) were treated and evaluated for efficacy and safety of AS and SOX. As of the data cutoff, the median follow-up was 23.13 months [95% confidence interval (CI), 13.39–32.87]. The median PFS was 9.03 months (95% CI, 6.50–11.56) in the AS group and 5.07 months (95% CI, 4.33–5.81) in the SOX group, demonstrating a better PFS tendency following AS treatment than SOX treatment (hazard ratio = 0.59; 95% CI, 0.37–0.94; p = 0.03). The most common grade 3 or worse adverse events were anemia, neutropenia, and leukopenia in both groups, with a higher incidence of thrombocytopenia in the SOX group.

Conclusion:

Although this study was terminated early, the results demonstrated a better PFS tendency in patients with AGC who were treated with AS than in those treated with SOX, with controllable toxicities.

Trial registration:

Clinical Trials.gov identifiers: NCT03801668. Registered January 11, 2019.

Evaluation of the in vitro Activity and in vivo Efficacy of Anidulafungin-Loaded Human Serum Albumin Nanoparticles Against Candida albicans

Recent decades have seen a significant increase in invasive fungal infections, resulting in unacceptably high mortality rates. Anidulafungin (AN) is the newest echinocandin and appears to have several advantages over existing antifungals. However, its poor water solubility and burdensome route of administration (i.e., repeated, long-term intravenous infusions) have limited its practical use. The objective of this study was to develop anidulafungin-loaded Human Serum Albumin (HSA) nanoparticles (NP) so as to increase both its solubility and antifungal efficacy. HSA was reduced using SDS and DTT, allowing liberation of free thiols to form the intermolecular disulfide network and nanoassembly. Reduced HSA was then added to MES buffer (0.1 M, pH 4.8) and magnetically stirred at 350 rpm and 25°C with AN (m/m 50:1) for 2 h to form nanoparticles (AN NP). We next performed routine antifungal susceptibility testing of Candida strains (n = 31) using Clinical and Laboratory Standards Institute (CLSI) methodologies. Finally, the in vivo efficacy of both AN and AN NP was investigated in a murine model of invasive infection by one of the most common fungal species—C. albicans. The results indicated that our carrier formulations successfully improved the water solubility of AN and encapsulated AN, with the latter having a particle size of 29 ± 1.5 nm with Polymer dispersity index (PDI) equaling 0.173 ± 0.039. In vitro AN NP testing revealed a stronger effect against Candida species (n = 31), with Minimum Inhibitory Concentration (MIC) values 4- to 32-fold lower than AN alone. In mice infected with Candida and having invasive candidiasis, we found that AN NP prolonged survival time (P < 0.005) and reduced fungal burden in kidneys compared to equivalent concentrations of free drug (P < 0.0001). In conclusion, the anidulafungin nanoparticles developed here have the potential to improve drug administration and therapeutic outcomes for individuals suffering from fungal diseases.

A natural protein based platform for the delivery of Temozolomide acid to glioma cells

Glioblastoma is one of the most difficult to treat cancers with poor prognosis and survival of around one year from diagnosis. Effective treatments are desperately needed. This work aims to prepare temozolomide acid (TMZA) loaded albumin nanoparticles, for the first time, to target glioblastoma (GL261) and brain cancer stem cells (BL6). TMZA was loaded into human serum albumin nanoparticles (HSA NPs) using the desolvation method. A response surface 3-level factorial design was used to study the effect of different formulation parameters on the drug loading and particle size of NPs. The optimum conditions were found to be: 4 mg TMZA with 0.05% sodium cholate. This yielded NPs with particle size and drug loading of 111.7 nm and 5.5% respectively. The selected formula was found to have good shelf life and serum stability but with a relatively fast drug release pattern. The optimized NPs showed excellent cellular uptake with ∼ 50 and 100% of cells were positive for NP uptake after 24 h incubation with both GL261 and BL6 glioblastoma cell lines, respectively. The selected formula showed high cytotoxicity with ̴ 20% cell viability at 1 mM TMZA after 72 h incubation time. Finally, the fluorescently labelled NPs showed co-localization with the bioluminescent syngeneic BL6 intra-cranial tumour mouse model after intravenous administration.

Insights into Multifunctional Nanoparticle-Based Drug Delivery Systems for Glioblastoma Treatment

Glioblastoma (GB) is an aggressive cancer with high microvascular proliferation, resulting in accelerated invasion and diffused infiltration into the surrounding brain tissues with very low survival rates. Treatment options are often multimodal, such as surgical resection with concurrent radiotherapy and chemotherapy. The development of resistance of tumor cells to radiation in the areas of hypoxia decreases the efficiency of such treatments. Additionally, the difficulty of ensuring drugs effectively cross the natural blood-brain barrier (BBB) substantially reduces treatment efficiency. These conditions concomitantly limit the efficacy of standard chemotherapeutic agents available for GB. Indeed, there is an urgent need of a multifunctional drug vehicle system that has potential to transport anticancer drugs efficiently to the target and can successfully cross the BBB. In this review, we summarize some nanoparticle (NP)-based therapeutics attached to GB cells with antigens and membrane receptors for site-directed drug targeting. Such multicore drug delivery systems are potentially biodegradable, site-directed, nontoxic to normal cells and offer long-lasting therapeutic effects against brain cancer. These models could have better therapeutic potential for GB as well as efficient drug delivery reaching the tumor milieu. The goal of this article is to provide key considerations and a better understanding of the development of nanotherapeutics with good targetability and better tolerability in the fight against GB.

Nanotechnology, in silico and endocrine-based strategy for delivering paclitaxel and miRNA: Prospects for the therapeutic management of breast cancer

Breast cancer is one of the most prevalent and reoccurring cancers and the second most common reason of death in women. Despite advancements in therapeutic strategies for breast cancer, early tumor recurrence and metastasis in patients indicate resistance to chemotherapeutic medicines, such as paclitaxel due to the abnormal expression of ER and EGF2 in breast cancer cells. Therefore, the development of alternatives to paclitaxel is urgently needed to overcome challenges involving drug resistance. An increasing number of studies has revealed miRNAs as novel natural alternative substances that play a crucial role in regulating several physiological processes and have a close, adverse association with several diseases, including breast cancer. Due to the therapeutic potential of miRNA and paclitaxel in cancer research, the current review focuses on the differential roles of various miRNAs in breast cancer development and treatment. miRNA delivery to a specific target site, the development of paclitaxel and miRNA formulations, and nanotechnological strategies for the delivery of nanopaclitaxel in the management of breast cancer are discussed. These strategies involve improving the cellular uptake and bioavailability and reducing the toxicity of free paclitaxel to achieve accumulation tumor site. Furthermore, a molecular docking study was performed to ascertain the enhanced anticancer activity of the nanoformulation of ANG1005 and Abraxane. An in silico analysis revealed that ANG1005 and Abraxane nanoformulations have superior and significantly enhanced interactions with the proteins α-tubulin and Bcl-2. Therefore, ANG1005 and Abraxane may be more suitable in the therapeutic management of breast cancer than the existing free paclitaxel. miRNAs can revert abnormal gene expression to normalcy; since miRNAs serve as tumor suppressors. Therefore, restoration of particular miRNAs levels as a replacement therapy may be an effective endocrine potential strategy for treating ER positive/ negative breast cancers.

Efficacy of Eribulin mesylate in older patients with breast cancer: A pooled analysis of clinical trial and real-world data

PURPOSE

Eribulin mesylate (EM) is a non-taxane microtubule inhibitor approved for use in patients with metastatic breast cancer. With this pooled analysis of retrospective studies, we evaluated the efficacy and toxicity profile of EM in older patients with breast cancer in the real-world setting.

METHODS

We performed a systematic database search for studies published up to March 2019 and reporting outcome and adverse events with EM in older patients (≥70 years). Overall survival (OS), progression-free survival (PFS), and overall response rate (ORR) were described and aggregated in a pooled analysis. Main toxicity rates (G1-2 and G3-4) were also described.

RESULTS

The analysis included five studies for a total of 301 patients. The median age was 71 to 74 years. Pooled ORR, median PFS and OS were 23.2%, 4.8 and 13.1 months, respectively. The disease control rate was 47%. Grade 3-4 neutropenia was 0 to 49%, G3-4 anemia and thrombocytopenia were rare. The most frequent G3-4 adverse events among non-hematological toxicities were fatigue (5-16.5%) and neurotoxicity (0-10.1%). Dose reduction rate was reported in three studies and carried out in 40% of patients (18.6-84%).

CONCLUSIONS

This pooled analysis shows that the median OS in older patients with breast cancer is 13 months, with an ORR of 23%. Control of disease was achieved in about 50% of patients. Dose reduction was relatively frequent and severe toxicities were rare. EM treatment of older patients with breast cancer is feasible and reflects the outcomes for the general population.

Efficacy and Safety of Nanoparticle Albumin-Bound Paclitaxel in Elderly Patients with Metastatic Breast Cancer: A Meta-Analysis

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is an approved treatment for metastatic breast cancer (MBC). However, there is an ongoing debate about the efficacy and safety of nab-paclitaxel in elderly patients. We conducted a meta-analysis to evaluate nab-paclitaxel efficacy and adverse events in MBC patients 65 years and older, compared with MBC patients younger than 65 years (control group). We performed a literature search using PubMed, the Cochrane Library, and EMBASE, from their inception to 30 September 2019. The relevant studies compared overall response rates (ORRs) and incidence of adverse events; four studies comprising 1204 patients were identified and included. ORRs were similar in patients older than 65 years and controls (odds ratio (OR) 0.71, 95% confidence interval (CI) 0.42-1.21). On subgroup analysis, both first-line therapy (OR 2.54, 95% CI 1.92-3.36) and lower Eastern Cooperative Oncology Group (ECOG) performance status (OR 0.20, 95% CI 0.06-0.69) were associated with a higher ORR. Adverse events including neutropenia, sensory neuropathy, diarrhea, and nausea were comparable between the groups. In conclusion, nab-paclitaxel showed comparable efficacy and safety in older and younger patients with MBC. Nab-paclitaxel can be a first-line treatment option for MBC patients 65 years and older.

Nab-paclitaxel in pretreated metastatic breast cancer: evaluation of activity, safety, and quality of life

Objective

Metastatic breast cancer (MBC) is an incurable disease; the treatment of this disease prolongs survival, improving the quality of life (QoL) with a balance between efficacy and toxicity of the treatment. In recent years, treatment with nab-paclitaxel has improved the already known antitumor activity of conventional paclitaxel, in terms of increased efficacy and better tolerability. The aim of this study was to evaluate nab-paclitaxel in Italian patients with MBC.

Methods

We conducted a retrospective analysis of 90 patients with histologically confirmed diagnosis of MBC. To evaluate the efficacy of nab-paclitaxel, overall survival (OS), progression-free survival (PFS), and overall response rate were the primary endpoints, whereas carbohydrate antigen 15.3 (Ca15.3) reduction, QoL, and tolerability were secondary endpoints.

Results

The median OS was 10.4 months, the median PFS was 6.8 months. A considerable difference Ca15.3 before and after treatment was observed. Descriptive and regression analyses were done to examine the associations between Ca15.3 response and OS, demonstrating good correlation, revealing that Ca15.3 reduction is an important predictor of OS.

Conclusion

Nab-paclitaxel is an effective and well-tolerated treatment of patients affected by MBC. The drug showed an improved tolerability profile. With all the limitations of the observational nature of our results, nab-paclitaxel has proven to be an effective and safe therapeutic option in patients with MBC.

Docetaxel-loaded human serum albumin (HSA) nanoparticles: synthesis, characterization, and evaluation

Background

Docetaxel (DTX) is an anticancer drug that is currently formulated with polysorbate 80 and ethanol (50:50, v/v) in clinical use. Unfortunately, this formulation causes hypersensitivity reactions, leading to severe side-effects, which have been primarily attributed to polysorbate 80.

Methods

In this study, a DTX-loaded human serum albumin (HSA) nanoparticle (DTX-NP) was designed to overcome the hypersensitivity reactions that are induced by polysorbate 80. The methods of preparing the DTX-NPs have been optimized based on factors including the drug-to-HSA weight ratio, the duration of HSA incubation, and the choice of using a stabilizer. Synthesized DTX-NPs were characterized with regard to their particle diameters, drug loading capacities, and drug release kinetics. The morphology of the DTX-NPs was observed via scanning electron microscopy (SEM) and the successful preparation of DTX-NPs was confirmed via differential scanning calorimetry (DSC). The cytotoxicity and cellular uptake of DTX-NPs were investigated in the non-small cell lung cancer cell line A549 and the maximum tolerated dose (MTD) of DTX-NPs was evaluated via investigations with BALB/c mice.

Results

The study showed that the loading capacity and the encapsulation efficiency of DTX-NPs prepared under the optimal conditions was 11.2 wt% and 63.1 wt%, respectively and the mean diameter was less than 200 nm, resulting in higher permeability and controlled release. Similar cytotoxicity against A549 cells was exhibited by the DTX-NPs in comparison to DTX alone while higher maximum tolerated dose (MTD) with the DTX-NPs (75 mg/kg) than with DTX (30 mg/kg) was demonstrated in mice, suggesting that the DTX-NPs prepared with HSA yielded similar anti-tumor activity but were accompanied by less systemic toxicity than solvent formulated DTX.

Conclusions

DTX-NPs warrant further investigation and are promising candidates for clinical applications.

Eribulin in Heavily Pretreated Metastatic Breast Cancer Patients in the Real World: A Retrospective Study

OBJECTIVES

The aim of this study was to investigate efficacy and safety of eribulin in heavily pretreated patients with advanced breast cancer (BC) in a real-life setting.

METHODS

This retrospective monocentric study included patients with HER-2-negative metastatic BC, pretreated with anthracyclines and taxanes, who were referred to the Oncology Department of Spedali Civili of Brescia from May 2012 to April 2017. Patients received the same dose of eribulin as that used in the EMBRACE trial: 1.4 mg/m2 on days 1 and 8 every 21 days.

RESULTS

In a total of 53 patients, 32% obtained a partial response, 11% a stable disease, and 43% a clinical benefit (CB). After a median follow-up of 36 months, median progression-free survival (PFS) was 4.7 months and median overall survival (OS) 13.53 months. Median PFS was significantly longer in patients who reported a CB compared to those with no CB, while survival outcomes (PFS and OS) were better in patients who received > 6 cycles of eribulin. Eribulin showed a good tolerability profile with acceptable toxicities, similar to those reported in EMBRACE.

CONCLUSIONS

Our experience in a real-world setting confirms the activity, efficacy, and good tolerability profile of eribulin in heavily pretreated BC patients.

Application of the CRISPR/Cas9 System to Drug Resistance in Breast Cancer

Clinical evidence indicates that drug resistance is a great obstacle in breast cancer therapy. It renders the disease uncontrollable and causes high mortality. Multiple mechanisms contribute to the development of drug resistance, but the underlying cause is usually a shift in the genetic composition of tumor cells. It is increasingly feasible to engineer the genome with the clustered regularly interspaced short palindromic repeats (CRISPR)/associated (Cas)9 technology recently developed, which might be advantageous in overcoming drug resistance. This article discusses how the CRISPR/Cas9 system might revert resistance gene mutations and identify potential resistance targets in drug-resistant breast cancer. In addition, the challenges that impede the clinical applicability of this technology and highlight the CRISPR/Cas9 systems are presented. The CRISPR/Cas9 system is poised to play an important role in preventing drug resistance in breast cancer therapy and will become an essential tool for personalized medicine.

Triple negative breast cancer: the kiss of death

One of the most controversial women malignancies, triple negative breast cancers (TNBCs) are critically overviewed here, being focused on data useful in clinical practice or to improve the therapy and patients survival. TNBCs "choose" young women and its "kiss" is, unfortunately deadly in most cases. Currently, few sparse data are available in literature concerning the origins of TNBC. Vasculogenic mimicry detected in TNBCs, seems to be determined by a population of CD133+ cells and may be stimulated by different pharmacological agents such sunitinib. Despite the fact that TNBCs do not usually metastasize through the lymphatic pathways, TNBCs may be characterized by lymphatic invasion and by an increased lymphatic microvascular density. If TNBCs treatment depends on the molecular profile of the tumor, the same statement may be postulated for TNBCs metastasis. Whether metastases have a similar phenotype as the primary tumor remains an enigma. Therefore, the question: 'Could TNBC be subject to a standardized, unanimously accepted therapeutic strategy or is it strictly subclass-dependent?' remains to be further investigated.

Eribulin for metastatic breast cancer (MBC) treatment: a retrospective, multicenter study based in Campania, south Italy (Eri-001 trial)

BACKGROUND

On the basis of the results of two pivotal phase III clinical trials, eribulin mesylate is currently approved in EU for the treatment of advanced breast cancer (aBC) in patients who have previously received an anthracycline and a taxane in either the adjuvant or the metastatic setting, and at least one chemotherapeutic regimen for metastatic disease.

METHODS

In our study, we investigated the efficacy and tolerability of eribulin as second or further line chemotherapy in 137 women affected by aBC.

RESULTS

Eribulin as monotherapy provided benefit in terms of progression-free survival (PFS), response rate (RR) and disease control rate (DCR) independently of its use as second or late-line therapy. The overall RR and DCR were 17.5% and 64%, respectively. In particular, DCR and overall RR were 50% and 13.6%, 65.4% and 21.1%, 70.4% and 14.8% and 66.7% and 16.7% in second, third, fourth and further lines of treatment, respectively. Median PFS (mPFS) according to the line of therapy was 5.7, 6.3, 4.5 and 4.0 months in patients treated with eribulin in second, third, fourth and over the fourth line, respectively. No significant difference in terms of mPFS was found between the various BC subtypes. Overall, eribulin resulted safe and most adverse events were of grade 1 or 2 and easily manageable. Grades 3-4 toxicities were neutropaenia and neurotoxicity.

CONCLUSIONS

With the limitations due to the observational nature of our findings, eribulin was shown to be an effective and safe therapeutic option in heavily pretreated patients with aBC.

Nonionic Microemulsions as Solubilizers of Hydrophobic Drugs: Solubilization of Paclitaxel

The strategy using nonionic microemulsion as a solubilizer for hydrophobic drugs was studied and is demonstrated in this work. The aqueous phase behaviors of mixed nonionic surfactants with various oils at 37 °C are firstly constructed to give the optimal formulations of nonionic microemulsions with applications in the enhanced solubilization of the model hydrophobic drug, paclitaxel, at 37 °C. Briefly, the suitable oil phase with paclitaxel significantly dissolved is microemulsified with appropriate surfactants. Surfactants utilized include Tween 80, Cremophor EL, and polyethylene glycol (4.3) cocoyl ether, while various kinds of edible oils and fatty esters are used as the oil phase. On average, the apparent solubility of paclitaxel is increased to ca. 70-100 ppm in the prepared microemulsions at 37 °C using tributyrin or ethyl caproate as the oil phases. The sizes of the microemulsions attained are mostly from ca. 60 nm to ca. 200 nm. The cytotoxicity of the microemulsion formulations is assessed with the cellular viability of 3T3 cells. In general, the cell viability is above 55% after 24 h of cultivation in media containing these microemulsion formulations diluted to a concentration of total surfactants equal to 50 ppm and 200 ppm.