Janes TA, Cardani S, Saini JK, Pagliardini S (2024) Etonogestrel promotes respiratory recovery in an in vivo rat model of central chemoreflex impairment. Acta Physiol (Oxf) e14093. doi: 10.1111/apha.14093 PMID: 38258900
Objective: Examine the use of progestins and synthetic progestins in the stimulation of breathing, especially after chemoreflexive impairment.
Summary: Central CO2 chemoreflex is important for respiratory control. The retrotrapezoid nucleus is involved in CO2 chemosensitivity where its removal or inhibition attenuates CO2 chemoreflexes and diminishes restful breathing. Progesterone stimulates restful breathing and CO2 chemoreflexes. The authors investigated whether acute or chronic administration of the progestinic drug, etonogestrel, could help in the recovery of respiratory chemoreflexes following lesion of the retrotrapezoid nucleus via a SP-SAP.
Usage: Rats were injected with 26-43.3 ng/ul of SP-SAP (IT-11) or 46.7 ng/ul of Blank-SAP (IT-21), with 150 nl per injection.
Maiarù M, Leese C, Silva-Hucha S, Fontana-Giusti S, Tait L, Tamagnini F, Davletov B, Hunt SP (2024) Substance P-botulinum mediates long-term silencing of pain pathways that can be re-instated with a second injection of the construct in mice. J Pain 11 doi: 10.1016/j.jpain.2024.01.331 PMID: 38218509
Summary: The authors discuss how Substance P-Botulinum is used to try to replicate the permanent results achieved with Substance P-Saporin (SP-SAP, SSP-SAP).
Yaksh TL, dos Santo G, Lemes J, Malange K (2023) Neuraxial drug delivery in pain management: An overview of past, present, and future. Anaesthesiology doi: 10.1016/j.bpa.2023.04.003
Objective: Activation of neuraxial nociceptive linkages leads to a high level of encoding of the message that is transmitted to the brain and that can initiate a pain state with its attendant emotive covariates. The authors review the encoding of this message and describe the how it is subject to regulation by pharmacological targeting of dorsal root ganglion and dorsal horn systems.
Summary: Authors provide an overview of the past, present and future directions of the biology, pharmacology and technology relevant to the use of the neuraxial route. SP-SAP was used as a neuraxial toxin to eliminate NK1R expressing cells, which characteristic of neurons known to be the second order neurons responding to C fiber input. Delivery of SP-SAP results in long-lasting loss of NK1 bearing dorsal horn neurons and analgesia.
Puente BR (2021) Chronic pain in dogs (Dolor crónico en el perro). Zaragoza Spain: Gruppo Asis Biomedia, S. L..
Summary: The author presents a thorough overview of aspects of canine chronic pain. He includes SP-SAP (Substance P-Saporin) as an experimental drug, “its use as an adjuvant analgesic in dogs with bone cancer has been studied,”
Vetter I (2018) Toxins in Neurobiology: New tools from old molecules. Neurosci Lett 679:1-3. doi: 10.1016/j.neulet.2018.05.008
Summary: The selective ablation of neurokinin-1 receptor-expressing neurons by SP-SAP revealed a key role for the preBötzinger complex in the generation of respiratory rhythm. Toxin-mediated neuronal ablation may also find therapeutic applications, such as the treatment of severe refractory pain in terminally ill patients by intrathecal SP-SAP which causes selective loss of neurokinin-1 receptor-expressing neurons in the spinal cord dorsal horn.
Over the years, ATS has frequently been asked about Saporin’s safety for use in the lab as well as when used clinically. Residual awareness of alternate Ribosome-Inactivating Proteins (RIPs) and ‘toxins’ such as Ricin have caused some researchers new to the use of RIPs to question the belief that Saporin is safe. Unlike Type 2 RIPs (such as Ricin), Type I RIPs, like Saporin have no binding chain and consequently no means of entering the physiological space necessary for the protein to act as a toxin. The following is a review of safety in handling and potential toxicity within the human body for systemic events not related to normal research applications of Saporin conjugates, including Substance P-Saporin (SP-SAP), which is a therapeutic under development for the treatment of chronic pain.
The acute LD50 for saporin in mice (25 g) is 6.8 mg/kg;[1] that would translate in humans (75 kg) to 510 mg! A concentration of about 100 nM is the threshold to see even a vague hint of saporin toxicity. In human blood, that would correspond to 24 mg injected systemically into a person. The fermentation process to produce recombinant saporin has a titer of 2 mg/L meaning that the production broth itself contains no more than 67 nM concentration of saporin. Furthermore, the final protein concentrations from production batches of recombinant Saporin used in our drug are 4 mg/ml, meaning 6 mL of final material would need to accidentally end up in a human before the ‘hint of toxicity’ threshold would potentially be met.
The toxicology studies of SP-SAP contained within ATS’s IND prior to the current human Phase I clinical trial evaluated effects related to the intended method of administration, intrathecal local injection. SP-SAP is not expected to ever be a self-administered therapy, so the effects of gross off-target events, such as accidental auto-injection, swallowing, spillage, or immersion were not considered.
The table below[2] highlights antibody-saporin conjugates approved by the FDA for Phase I/II clinical trials in humans. The therapeutics listed below were administered intravenously and imply what the FDA accepted as non-toxic levels of saporin-based conjugates in these studies.
Looking more closely at the study by French et al.,[3] several milligrams of antibody conjugate were repeatedly injected into human patients under a FDA regulated clinical trial and peak serum levels tested, demonstrating rapid clearing of saporin from the system.
As a company that specializes in Saporin, our two-plus decades of experience working with the protein in research, preclinical, and clinical environments has taught us that with minimal standard laboratory precautions users are not at any real risk of toxic effects. Even our CSO, after 30+ years of working with Saporin exhibits undetectable levels of Saporin antibodies in his blood!
Pergolizzi J, Gharibo C, Ho K (2015) Treatment considerations for cancer pain: A global perspective. Pain Pract 15:778-792. doi: 10.1111/papr.12253
Summary: This review discusses the treatment of cancer pain, addressing various aspects of the overall picture, such as early pain treatment to reduce central sensitization and chronic pain, pain assessment tools, and guidelines for treating specific populations of patients. Some of the current tools for pain management are discussed, including SP-SAP, which is currently in clinical trials as a cancer pain therapeutic.
Frankel AE, Nymeyer H, Lappi DA, Higgins D, Ahn C, Noe C (2014) Preliminary results from a phase I study of substance P-saporin in terminal cancer patients with intractable pain. Journal of Clinical Oncology 32:191. doi: 10.1200/jco.2014.32.31_suppl.191
Summary: Existing pain therapies are insufficient to control cancer pain in 10-15% of patients. Substance P (SP) and its receptor, neurokinin-1 (NK-1r) have been determined to play a major role in spinal transmission of chronic pain. Animal studies have demonstrated that disruption of the NK-1r pathway alleviates chronic pain caused by a variety of stimuli. The authors are conducting a Phase I clinical trial in humans (NCT02036281) assessing the ability of SP-SAP (Cat. #IT-07) to treat intractable chronic pain due to cancer. Patients have received intrathecal injections of 1, 2, or 4 µg of SP-SAP with no evidence of toxicity or neurological or cardiac abnormalities. Doses will escalate up to 90 µg.
Q: How long does it take to see the cell death occurring from the use of targeted toxins using saporin? Is there a time course of hours or days?
A: The figure below illustrates the time course of cell death very effectively. Internalization and cytotoxicity of SP-SAP in primary cultures of neonatal spinal cord neurons. Confocal image of neurons where the Substance P receptor; NK1R (SPR) immunofluorescence (A, C, D) appears red, areas of concentrated SPR immunofluorescence appear yellow. (A, C, and D) SPR immunofluorescence in neurons 2 hours, 1 day, and 4 days, respectively, after treatment with SP-SAP. (B) Confocal image showing SAP immunofluorescence (yellow) 2 hours after SP-SAP treatment.
These images were projected from 14 optical sections acquired at 0.8-mm intervals with a 603 lens. Bar, 25 mm.
It is recommended that you wait for two weeks to allow for all debris to be cleared and the animal to regain normal eating and sleeping habits.
