Pirtobrutinib (LOXO-305) HCl

BTK (Bruton's tyrosine kinase), non-covalent inhibitor

Pirtobrutinib (LOXO-305) is a next-generation Bruton's tyrosine kinase (BTK) inhibitor that is highly selective, non-covalent, and exhibits strong equilibrium binding to both WT BTK and several BTK C481 substitution mutations.It also potently inhibits the cellular activity of BTK C481S, T, and R mutations.[2]

Pirtobrutinib significantly inhibits tumor growth in human lymphoma xenografts in vivo. [3]

Pirtobrutinib activity against BTK, BTK C481S, and selected non-BTK kinases was determined by monitoring incorporation of [33P]-PO4 from [33P]-adenosine triphosphate (ATP) into polyglutamic acid–tyrosine (poly-EY) peptide substrate in the HotSpot Kinase Assay (Reaction Biology, Malvern, PA).25 Data were analyzed using standard-curve fitting methods. Pirtobrutinib (1 μM) was tested for kinase activity inhibition of 371 human kinases using the HotSpot Kinase Assay and Km ATP concentrations. Pirtobrutinib, ibrutinib, zanubrutinib, and acalabrutinib (100 nM) were tested using the HotSpot Kinase Assay at a concentration of 10 μM ATP. Percentage of control activity was calculated for each enzyme.[3]

HEK293T cell lines that were transiently expressing WT BTK and BTK C481 substitution mutations were treated for 30 minutes with LOXO-305, ibrutinib, or acalabrutinib before orthovanadate was added. Following a 2-hour incubation period, cells were lysed, and total BTK and phosphorylated Y223 BTK were identified using MesoScale (C481R) or immunoblot (BTK WT, C481S, and C481T). Using GraphPad Prism, the bands and MSD signals were quantified and the IC50 values were computed.

OCI-Ly10 cells were implanted subcutaneously into male nonobese diabetic/severe combined immunodeficiency mice and tumors were allowed to grow to a volume of between ∼150 and 200 mm3. Mice were randomized by tumor size across dose groups and dosed orally twice-daily (BID) with 10 or 50 mg/kg pirtobrutinib (12 mice per group) or vehicle (11 mice per group) for 28 days. Tumor volumes were measured thrice weekly during the study and for an additional 35 days after dosing (Axis Bioservices, Coleraine, United Kingdom). In the TMD8 study, cells were injected subcutaneously into Balb/c SCID mice and allowed to grow for 19 days until a mean tumor volume of 400 mm3 was reached. Mice were randomized by tumor size across dose groups and orally dosed BID with 15 or 30 mg/kg pirtobrutinib (10 mice per group) for 18 days or vehicle (10 mice per group) for 14 days. Tumor volumes were measured thrice weekly. REC-1 cells were injected subcutaneously into female athymic nude mice and allowed to grow for 18 days when a mean tumor volume of 150 mm3 was reached. Mice were randomized by tumor volume across dose groups and orally dosed BID with pirtobrutinib at 10, 30, or 50 mg/kg (6 mice per group) or vehicle (10 mice per group) for 21 days. Tumor volumes were measured twice weekly. TMD8 cells expressing BTK C481S were injected into female Balb/c SCID mice and allowed to grow for 12 days when a mean tumor volume of 150 mm3 was reached. Mice were randomized by tumor size and orally dosed BID with pirtobrutinib at 3, 10, and 30 mg/kg (10 mice per group) or vehicle (14 mice per group) for 14 days. Tumor volumes were measured 2 or 3 times per week. Animal procedures for the OCI-Ly10 xenograft tumor studies were performed under the guidance of the United Kingdom Animal (Scientific Procedures) Act 1986. Mice used in the TMD8 and TMD8 BTK C481S studies were treated in accordance with guidelines by the Association for Assessment and Accreditation of Laboratory Animal Care International, and protocols were authorized by the French Ministry of Education, Advanced Studies and Research. All procedures used in the REC-1 xenograft study were compliant with the United States Department of Agriculture’s Animal Welfare Act (9 CFR Parts 1, 2, and 3) and the Guide for the Care and Use of Laboratory Animals (Institute for Laboratory Animal Research, The National Academies Press, Washington, DC).[3]

[1]. Blood (2019) 134 (Supplement_1): 478.
[2]. Blood (2019) 134 (Supplement_1): 4644.
[3]. Blood . 2023 Jul 6;142(1):62-72.
[4]. J Clin Oncol. 2015; 35:1437-1443.
[5]. Haematologica. 2018; 103(5):874-879.

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

---

Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

View More

Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

---

Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

View More

Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

---

Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

---

 (Please use freshly prepared in vivo formulations for optimal results.)