- Molecular FormulaC61H67N9O17S4
- Average mass1326.495 Da
2-(2-(2-(4-((2S)-2-(4-(((2-amino-4-oxo-3,4-dihydropteridin-6-yl)methyl)amino)benzamido)-2-carboxyethyl)phenoxy)-3-(2-(3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-1,3-dihydro-2H-indol-2-ylidene)ethylidene)cyclohex-1-en-1-yl)ethenyl)-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium inner salt,sodium salt (1:4)
3H-Indolium, 2-(2-(2-(4-((2S)-2-((4-(((2-amino-3,4-dihydro-4-oxo-6-pteridinyl)methyl)amino)benzoyl)amino)-2-carboxyethyl)phenoxy)-3-(2-(1,3-dihydro-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-2H-indol-2-ylidene)ethylidene)-1-cyclohexen-1-yl)ethenyl)-3,3-dimethyl-5-sulfo-1 (4-sulfobutyl)-, inner salt,sodium salt (1:4)
Pafolacianine sodium [USAN]
Intraoperative Imaging and Detection of Folate Receptor Positive Malignant Lesions
The most common side effects of pafolacianine include infusion-related reactions, including nausea, vomiting, abdominal pain, flushing, dyspepsia, chest discomfort, itching and hypersensitivity.
The safety and effectiveness of pafolacianine was evaluated in a randomized, multi-center, open-label study of women diagnosed with ovarian cancer or with high clinical suspicion of ovarian cancer who were scheduled to undergo surgery. Of the 134 women (ages 33 to 81 years) who received a dose of pafolacianine and were evaluated under both normal and fluorescent light during surgery, 26.9% had at least one cancerous lesion detected that was not observed by standard visual or tactile inspection.
The U.S. Food and Drug Administration (FDA) granted the application for pafolacianine orphan drug, priority review, and fast track designations. The FDA granted the approval of Cytalux to On Target Laboratories, LLC.
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In another aspect of the invention, this disclosure provides a method of synthesizing a compound having the formula
 In a fourth embodiment of the invention, this disclosure provides a method of synthesizing a compound having the formula
 wherein C is any carbon isotope. In this embodiment, the amino acid linker is selected from a group consisting of methyl 2-di-tert-butyl dicarbonate-amino-3-(4-phenyl)propanoate, 3-(4-hydroxyphenyl)-2-(di-tert-butyl-dicarbonate methylamino)propanoic acid, 2-amino-4-(4-hydroxyphenyl)butanoic acid, and Tert-butyl (2-di-tert-butyl dicarbonate- amino)-3-(4-hydroxyphenyl)propanoate . In a particular embodiment, the aqueous base is potassium hydroxide (KOH). The method of this embodiment may also further include purifying the compound by preparatory HPLC.
EXAMPLE 1 : General synthesis of Pte – L Tyrosine – S0456 (OTL-0038)
Reactants for Step I:
 A 500 mL round bottom flask was charged with a stirring bar, pteroic acid
(12.0 g, 29.40 mmol, 1 equiv), (L)-Tyr(-OfBu)-OfBu- HCI (1 1 .63 g, 35.28 mmol, 1 .2
equiv) and HATU (13.45 g, 35.28 mmol, 1 .2 equiv) then DMF (147 mL) was added to give a brown suspension [suspension A]. DIPEA (20.48 mL, 1 17.62 mmol, 4.0 equiv) was added slowly to suspension A at 23 °C, over 5 minutes. The suspension turned in to a clear brown solution within 10 minutes of addition of DIPEA. The reaction was stirred at 23 °C for 2.5 h. Reaction was essentially complete in 30 minutes as judged by LC/MS but was stirred further for 2.5 h. The formation of Pte_N10(TFA)_L_Tyr(-OfBu)-OfBu HCI (Figure 12) was confirmed by LC/MS showing m/z 409→m/z 684. LC/MS method: 0-50% acetonitrile in 20 mM aqueous NH4OAc for 5 min using Aquity UPLC-BEH C18, 1 .7μιη 2.1 * 50 mm column . The reaction mixture was cannulated as a steady stream to a stirred solution of aq. HCI (2.0 L, 0.28 M) over the period of 30 minutes to give light yellow precipitate of Pte_N10(TFA)_L_Tyr(-OfBu)-OfBu HCI. The precipitated Pte_N 10(TFA)_L_Tyr(- OfBu)-OfBu HCI was filtered using sintered funnel under aspirator vacuum, washed with water (8 * 300 mL) until the pH of the filtrate is between 3 and 4. The wet solid was allowed to dry under high vacuum for 12 hours on the sintered funnel. In a separate batch, where this wet solid (3) was dried under vacuum for 48 hours and then this solid was stored at -20 0 C for 48 h. However, this brief storage led to partial decomposition of 3. The wet cake (58 g) was transferred to a 500 mL round bottom flask and was submitted to the next step without further drying or purification.
Reactants for Step II:
The wet solid (58 g) was assumed to contain 29.40 mmol of the desired compound (3) (i. e. quantitative yield for the step I ).
 A 500 mL round bottom flask was charged with a stirring bar, Pte_N10(TFA)_L_Tyr(-OfBu)-OfBu HCI as a wet cake (58 g, 29.40 mmol, 1 equiv). A solution of TFA:TIPS:H20 (95:2.5:2.5, 200 mL) was added at once to give a light brown suspension. The reaction content was stirred at 23°C for 1 .5 hours and was monitored by LC/MS. The suspension became clear dull brown solution after stirring for 5 minutes. LC/MS method: 0-50% acetonitrile in 20 mM aqueous NH4OAc for 5 min using Aquity UPLC-BEH C18, 1 .7μιη 2.1 * 50 mm column. The formation of Pte_TFA_L_Tyr (Figure 12) was confirmed by showing m/z 684→m/z 572. Reaction time varies from 30 min to 1 .5 hours depending on the water content of Pte_N10(TFA)_L_Tyr(-OfBu)-OfBu HCI. The reaction mixture was cannulated as a steady stream to a stirred MTBE (1 .8 L) at 23 °C or 100 °C to give light yellow precipitate of Pte_TFA_L_Tyr. The precipitated Pte_TFA_L_Tyr was filtered using sintered funnel under aspirator vacuum, washed with MTBE (6 * 300 mL) and dried under high vacuum for 8 hours to obtain Pte_TFA_L_Tyr (14.98 g, 83.98% over two steps) as a pale yellow solid. The MTBE washing was tested for absence of residual TFA utilizing wet pH paper (pH between 3-4). The yield of the reaction was between 80-85% in different batches. The deacylated side product was detected in 3.6% as judged by LC/MS. For the different batches this impurity was never more than 5%.
Reactants for Step III:
 A 200 mL round bottom flask was charged with a stirring bar and Pte_TFA_L_Tyr (13.85 g, 22.78 mmol, 1 equiv), then water (95 mL) was added to give a yellow suspension [suspension B]. A freshly prepared solution of aqueous 3.75 M NaOH (26.12 mL, 97.96 mmol, 4.30 equiv), or an equivalent base at a corresponding temperature using dimethylsulfoxide (DMSO) as a solvent (as shown in Table 1 ), was added dropwise to suspension B at 23 °C, giving a clear dull yellow solution over 15 minutes [solution B]. The equivalence of NaOH varied from 3.3 to 5.0 depending on the source of 4 (solid or liquid phase synthesis) and the residual TFA. Trianion 5 (Figure 12) formation was confirmed by LC/MS showing m/z 572→m/z 476 while the solution pH was 9-10 utilizing wet pH paper. The pH of the reaction mixture was in the range of 9-10. This pH is crucial for the overall reaction completion. Notably, pH more than 10 leads to hydrolysis of S0456. Excess base will efficiently drive reaction forward with potential hydrolysis of S0456. The presence of hydrolysis by product can be visibly detected by the persistent opaque purple/blue to red/brown color.
TABLE 1 : Separate TFA deprotection via trianion formation; S0456
 The precipitated OTL-0038 product could also be crashed out by adding the reaction solution steady dropwise to acetone, acetonitrile, isopropanol or ethyl acetate/acetone mixture. Acetone yields optimal results. However, viscous reactions could be slower due to partial insolubility and/or crashing out of S0456. In this reaction, the equivalence of the aqueous base is significant. Excess base will efficiently drive reaction forward with potential hydrolysis of S0456. This solution phase synthesis provides Pte_N10(TFA)_Tyr-OH »HCI salt and desires approximately 4.1 to approximately 4.8 equiv base as a source to hydrolyze the product. Particularly, precipitation of Pte_Tyr_S0456 was best achieved when 1 mL of reaction mixture is added dropwise to the stirred acetone (20 mL). Filtration of the precipitate and washing with acetone (3 x10 mL) gave the highest purity as judged from LC/MS chromatogram.
 During experimentation of this solution-phase synthesis of Pte – L Tyrosine -S0456 (OTL-0038) at different stages, some optimized conditions were observed:
Mode of addition: Separate TFA deprotection via trianion formation; S0456 @ 23 °C; reflux.
Stability data of Pte – L Tyrosine – S0456 (OTL-0038):
Liquid analysis: At 40 °C the liquid lost 8.6% at 270 nm and 1 % at 774 nm. At room temperature the liquid lost about 1 .4% at 270 nm and .5% at 774 nm. At 5 °C the
270 nm seems stable and the 774 nm reasonably stable with a small degradation purity.
Source Purity Linker S0456 Base Solvent Duration % Conversion
95% 1 equiv equiv H20 15 min 100% phase equiv
FDA approves pafolacianine for identifying malignant ovarian cancer lesions
On November 29, 2021, the Food and Drug Administration approved pafolacianine (Cytalux, On Target Laboratories, LLC), an optical imaging agent, for adult patients with ovarian cancer as an adjunct for interoperative identification of malignant lesions. Pafolacianine is a fluorescent drug that targets folate receptor which may be overexpressed in ovarian cancer. It is used with a Near-Infrared (NIR) fluorescence imaging system cleared by the FDA for specific use with pafolacianine.
Efficacy was evaluated in a single arm, multicenter, open-label study (NCT03180307) of 178 women diagnosed with ovarian cancer or with high clinical suspicion of ovarian cancer scheduled to undergo primary surgical cytoreduction, interval debulking, or recurrent ovarian cancer surgery. All patients received pafolacianine. One hundred and thirty-four patients received fluorescence imaging evaluation in addition to standard of care evaluation which includes pre-surgical imaging, intraoperative palpation and normal light evaluation of lesions. Among these patients, 36 (26.9%) had at least one evaluable ovarian cancer lesion detected with pafolacianine that was not observed by standard visual or tactile inspection. The patient-level false positive rate of pafolacianine with NIR fluorescent light with respect to the detection of ovarian cancer lesions confirmed by central pathology was 20.2% (95% CI 13.7%, 28.0%).
The most common adverse reactions (≥1%) occurring in patients were nausea, vomiting, abdominal pain, flushing, dyspepsia, chest discomfort, pruritus, and hypersensitivity.
The recommended pafolacianine dose is 0.025 mg/kg administered intravenously over 60 minutes, 1 to 9 hours before surgery. The use of folate, folic acid, or folate-containing supplements should be avoided within 48 hours before administration of pafolacianine.
This application was granted priority review, fast track designation, and orphan drug designation. A description of FDA expedited programs is in the Guidance for Industry: Expedited Programs for Serious Conditions-Drugs and Biologics.
USFDA approves new drug to help identify cancer lesions
This drug is indicated for use in adult patients with ovarian cancer to help identify cancerous lesions during surgery.
|Chemical and physical data|
|Molar mass||1326.49 g·mol−1|
|3D model (JSmol)|
////////////Pafolacianine, FDA 2021, APPROVALS 2021, Cytalux, OVARIAN CANCER, OTL 38,