Reused Drugs to Fight Glioblastoma (part two)
Here we are in the eighth episode of the Ben Williams guide translation project on treatment options for Glioblastoma Multiforme. This is the second part of chapter 6 of the guide which, as I said, is very long and has been divided into parts. In this second part we talk about Disulfiram, Keppra, Methadone, proton pump inhibitors and Tamoxifen. There are several drugs, some of which have had interesting and sometimes decisive effects on some patients but somehow contradicting or disappointing in the different phases of the clinical trials. The outcome in the specific case depends on the specific mutations of the single glioblastoma. The advice is still to use this information to discuss it with the medical team that is following you presenting also the references to supporting scientific works.
The campaign launched on GoFund.me Glioblastoma.it for CUSP-ND for Emanuele is continuing. I ask you once again to share the link. As promised I will try to explain the costs of a clinical trial. During a clinical trial that is offered free to participants, one of the cost items is the purchase of drugs, for each patient, for the entire duration of the trial. If the prescribed drugs cost € 2000 per month and the trial lasts for 3 years, then € 72.000 are needed for each patient (€ 2000 x 12 x 3). If the trial involves 30 patients, more than € 2 million of drugs alone (€ 72.000 x 30) are needed. To this must be added other cost items (any additional personnel, any unforeseen analyses, etc.). I hope I was able to give you the idea. The positive side is that if the trial is successful it can become the new standard of care and the cost of the treatments then passes to the National Health Service. Enjoy the reading!
This old drug has been used for decades for the purpose of preventing alcohol consumption. Numerous researches in Germany have shown that it also has several anticancer properties. Regarding GBM treatment, one of its mechanisms is to block the glycoprotein pumps that extrude chemotherapeutic agents from the cell body before they have had a chance to be effective. It also inhibits the MGMT enzyme which allows the cell to repair damage from the treatment before the cell undergoes apoptosis (programmed cell death) and metalloproteinase activity, which is a primary mechanism by which GBM cells invade tissue. adjacent. Perhaps most importantly, it also inhibits the growth of stem cells, which are now believed to be the main source of treatment failures. This toxic drug has an effect enhanced by the concomitant use of copper gluconate, a common dietary supplement.
Disulfiram is currently being tested in a Phase I pharmacodynamic trial at Washington University, St. Louis, Missouri. This study consists of two arms: in one arm, patients are given one of two doses of disulfiram (500 mg or 1000 mg) per day along with their monthly temozolomide courses; in the second arm, 6 mg of copper gluconate is administered in combination with disulfiram and temozolomide. The results for the first arm (disulfiram and copper-free temozolomide) were published in the Journal of Neuro-oncology in early 2016 (332). Twelve patients were evaluated: seven on a 500 mg dose of disulfiram per day and five patients on 1000 mg per day. Two of the seven patients in the 500 mg group discontinued disulfiram treatment after 55 and 80 days due to delirium and peripheral motor neuropathy. Two of five patients in the 1000 mg per day group suffered from grade 3 delirium after 15 days of disulfiram and the maximum tolerated dose of disulfiram in combination with adjuvant temozolomide was determined to be 500 mg per day. The pharmacodynamic endpoint of the study was proteasome inhibition: there were minor reductions in proteasome activity in the whole blood of patients at week 4 (mean inhibition of 5% for the 500 mg dose and mean inhibition of 11% for the 1000 mg dose). At the time of the analysis, 9 of the 12 patients had had disease progression. Results for the study arm that received copper gluconate in addition to disulfiram have not yet been reported.
Keppra (levetiracetam) was approved by the FDA in 1999 as an antiepileptic drug and has since become perhaps the most commonly prescribed agent for the prevention of seizures in patients with brain tumors. Laboratory studies have shown that Keppra can inhibit the activity of the DNA repair enzyme MGMT and sensitize glioblastoma cells to chemotherapy with temozolomide (206). Furthermore, retrospective studies on patients with newly diagnosed glioblastoma show that the use of Keppra during chemotherapy can lead to a significant increase in progression-free and overall survival. In one of these studies by Korean researchers (323), 58 patients with glioblastoma who received Keppra for at least three months while on temozolomide chemotherapy were compared with 45 patients who received standard treatments without prolonged use of Keppra. Patients who received Keppra during chemotherapy had a median progression-free survival of 9.4 months compared to 6.7 months in the group not taking Keppra, a highly significant difference (HR = 0.42, p = 0.004 in the multivariate analysis). Similarly, overall survival was also extended in patients who received Keppra: median OS was 25.7 months compared to 16.7 months in patients who did not take Keppra (HR = 0.31, p = <0.001). It remains to be determined whether the apparent survival advantage for patients taking Keppra during standard chemotherapy is limited to patients with unmethylated MGMT status. The median OS was 25.7 months compared to 16.7 months in patients who did not take Keppra (HR = 0.31, p = <0.001).
An article published in 2014 by Claudia Friesen et al. from the University of Ulm, Germany, showed a chemosensitizing effect of methadone on glioma cells in vitro and in a mouse model of subcutaneous glioma (365). This document is based on previous preclinical work on the use of methadone plus doxorubicin in models of acute lymphoblastic leukemia. In these articles, the methadone stimulation of mu-opioid receptors expressed on cancer cells led to the blockade of adenyl cyclase and the consequent downregulation of cyclic adenosine monophosphate (cAMP). Since cAMP has protective effects against apoptosis, the overall result was a decreased expression of anti-apoptotic proteins and a significantly increased apoptosis when methadone was applied in combination with doxorubicin, a chemotherapeutic agent. In the previous publication (366) related to a glioma study, methadone alone led to a slightly reduced tumor growth rate in mice, but inexplicably methadone was not combined with chemotherapy in this experiment.
Methadone is an opioid drug indicated for the management of severe pain and as a replacement therapy for addiction to heroin or other morphine-like drugs. Due to the potential for addiction and abuse, methadone is a controlled substance in the United States. In most countries, methadone is most commonly used in the form of a racemic mixture, which means that it contains the molecule’s (R) and (S) enantiomers in equal proportions. These two forms of methadone are also known as levomethadone and dextromethadone and are mirror images of each other. Racemic methadone is therefore called (R, S) -methadone while right methadone or levomethadone is called D or L-methadone. The use of (R) -methadone for heroin addiction has become common in Germany, although not approved in the United States.
Although only the (R) -enantiomer has opioid receptor agonist activity, the racemic form containing both enantiomers in equal proportion is preferred by the authors of cancer studies as this effect is more pronounced with D, L-methadone since D-methadone stabilizes opioid receptors and thus facilitates greater binding of L-methadone. In addition, it has also been shown that the (S) -enantiomer, dextromethadone, has inhibitory activity against NMDA glutamate receptors, which are involved in seizure activity.
In 2017, a retrospective safety and tolerability study was published that provided details on 27 patients with newly diagnosed and recurrent glioma treated with methadone D, L (367). Of these, 12 newly diagnosed glioblastoma patients received methadone along with the Stupp standard of care regimen. The dose started with 5 drops twice a day (for a total of 5 mg per day) and gradually increased to a final dose of 15-35 mg per day (i.e. a maximum of 35 drops twice a day).
During the dose escalation period, nearly half of the patients experienced side effects, the most common of which was nausea. Side effects resolved in most cases after one month of methadone therapy. In three cases, constipation (constipation), a known side effect of opioid therapy, occurred after week 4.
The 12 newly diagnosed GBM patients treated with methadone in combination with standard treatments were considered in an efficacy analysis. The 6-month progression-free survival for this group was 91%. These results appear to be an improvement over historical data, although longer follow-up will be needed to determine if methadone actually has better efficacy.
In addition to this safety and tolerability study with very preliminary efficacy results, there are reports of some impressive tumor responses in refractory cancer patients with combinations of chemotherapy plus methadone.
Proton pump inhibitors
Cancer cells of all varieties thrive in an acidic environment. They also produce large amounts of lactic acid due to their dependence on anaerobic metabolism. Proton pumps are critically involved in the extrusion of intracellular acid into the extracellular microenvironment. Proton pump inhibitors, which have been developed for heartburn due to excess stomach acid, can interrupt this extrusion and thus suppress tumor growth. A number of recent evidence indicates that pretreatment of cancer cells with PPI causes cells to become much more sensitive to cytotoxic drugs (19) and also to DCA (126).
It is important to emphasize that the effect occurs only when the PPI is taken before treatment, because it takes 1-3 days to completely suppress the proton pump. Evidence of the clinical benefit of PPIs (in vivo) comes from a study in dogs and cats with various types of cancer. Thirty-four dogs and cats treated with lansoprazole (Prevacid) before regular chemotherapy were compared to 17 dogs and cats who received chemotherapy alone (127). Twenty-three of the patients who received the PPI achieved a complete or partial response, and the rest had disease stabilization and improved quality of life. Of the patients who received chemotherapy alone, only 3 (17%) had a partial (short-lived) response and the rest died due to disease progression within two months.
The clinical efficacy of proton pump inhibitors for human patients is supported by a Chinese study in metastatic breast cancer (128) which compared conventional chemotherapy alone with chemotherapy in combination with 100 mg nexium twice daily or in combination with 80 mg of nexium twice a day. Median PFS values were 7.5 months for those who received chemotherapy only, 9.5 months for those on the 100 mg dose, and 10.9 months for the 80 mg dose. The higher PFS value with the lower nexium dose suggests that lower doses may also be effective.
This drug is well known for its use in the treatment of breast cancer. Its mode of action is to compete with estrogen for attachment to the estrogen receptors of breast cells, thus reducing the ability of estrogen to act as a growth factor for carcinogenesis. This mode of action has little to do with tamoxifen’s ability to act as a therapeutic agent for gliomas. The effects on glioma are instead due to the fact that tamoxifen is an inhibitor of the activity of protein kinase C, an intracellular enzyme involved in the proliferation of glioma cells. Protein kinase C is now also known to play a significant role in the stimulation of angiogenesis. To obtain the inhibition of PKC activity and therefore slow down or stop the growth of cancer cells, very high doses of tamoxifen are used, in contrast to its use for breast cancer. The typical dosage for breast cancer is 10-20 mg per day, while for gliomas the dosage used has been between 160-240 mg per day. This high dosage is potentially problematic and has side effects. The most important is an increased risk of blood clots. For women, the risk of uterine cancer also increases and for men, impotence and loss of libido are frequent problems. Weight gain is another significant side effect. Overall, however, these side effects are mild compared to those of traditional chemotherapy.
A phase II clinical study (102) evaluating the effects of tamoxifen on patients with recurrent gliomas produced tumor regression in 25% of patients and stabilization of tumor growth for an additional 20% of patients. The percentage of patients responding to treatment was higher with grade III astrocytomas than that obtained in patients with GBM. The median survival time from the start of tamoxifen treatment was 16 months for grade III tumors and 7.2 months for glioblastomas. This perhaps appears to be a minimal benefit (survival time for recurrent glioblastomas typically ranges from 3-7 months when second-line chemotherapy is used) but it should also be noted that a percentage of those who have regressed or stabilized have been of survival greater than two years. Therefore, for the people who responded, tamoxifen produced a great benefit.
Tamoxifen was studied as a single agent, in combination with radiation, in a clinical study with 77 newly diagnosed glioblastomas at a dose of 80 mg / m2. (103). Median survival was 11.3 months, not significantly better than the results obtained with radiation alone. Long-term survival was not evident here, as only 9% of patients lived longer than two years.
Tamoxifen has also been used in conjunction with traditional chemotherapy, because in principle it should reduce the level of chemo-resistance as well as having its direct effects on tumor growth. A European clinical trial combined tamoxifen with carboplatin as an initial treatment after radiotherapy (104). Dosages of tamoxifen ranged from 40 to 120 mg / day, all lower than those used when tamoxifen was used alone (160-240 mg / day). Combined across all dosages, the 12-month and 24-month survival rates were 52 and 32%, respectively. For patients who received the highest tamoxifen dosage, the 12-month survival rate was 78%. In comparison, a matched group of subjects who received carboplatin alone after radiotherapy had 12- and 24-month survival rates of 30% and 0%. However, a second similar study combining tamoxifen with carboplatin (105) reported a median survival time of only 55 weeks, only slightly longer than historical controls using carboplatin alone (48 weeks). However, this latest study found that a minority of patients had unusually long survival times, which was not reflected in median survival times. The combination of carboplatin and tamoxifen has also been studied in patients with recurrent cancers. The median survival time here was 14 months, but only 6 months for the subgroup of 16 patients with GBM (106), which was not reflected in the median survival times.
Tamoxifen with a dosage of 240 mg / day has also been studied in combination with BCNU as an initial treatment after radiotherapy (107). Median survival time was 69 weeks, while 1-year, 2-year, and 3-year survival rates were 65%, 45%, and 24%, respectively. It should be noted that while the survival rate at 1 year and the median survival time are only marginally higher than those obtained with the BCNU alone, the 2 and 3 year survival times are substantially greater. Note, however, that these numbers are based on a small number of patients (N = 23). This advantage in terms of the number of long-term survivors again reflects the fact that tamoxifen is only effective for a minority of patients, but for them its benefits can be substantial. The fact that only a minority of patients benefit from tamoxifen is relevant to the negative results of a phase III study conducted in France (108). Patients received BCNU alone or BCNU in combination with tamoxifen 40-100 mg / day (note that these dosages are substantially lower than those used in the other studies). There was no increase in median survival time, while the addition of tamoxifen significantly increased the frequency of serious blood clots.
Several clinical trials have investigated tamoxifen in combination with Temodar. In a preliminary report (109), combined treatment, presented as the initial treatment after standard radiotherapy, resulted in all patients living 12 months after diagnosis. More details are clearly needed, but the results described are unusually promising. However, a second published study combining Temodar and tamoxifen (110) produced particularly negative results and was in fact terminated early due to the low response rate and frequency of toxicity. However, this toxicity most likely stemmed from the TMZ daily schedule used, which apparently included too high a dose for patients who had been heavily pretreated. An important feature of tamoxifen is that its toxicity to glioma cells is mainly due to its first metabolite, which takes 2-8 weeks to reach asymptotic levels. Therefore, it is likely that use for a short time, even with high dosages, is not effective.
A third study (111) combining tamoxifen with the standard Stupp protocol (N = 17) used a dose of 100 mg / m2 and reported a median survival of 17 months and a 2-year survival of 35%, slightly better than the Stupp protocol alone.
The most recent report (112) on the use of the combination of tamoxifen with temozolomide concerned recurrent cancers (N = 32) and used an alternate week program of temozolomide. Patients had previously received temozolomide according to the usual schedule. After the start of the new tamoxifen combination program, the median time to tumor progression was 7 months and the median survival time was 17.5 months, unusually high for recurrent cancers. The tamoxifen dose was 80 mg / m2. Furthermore, the authors reported no differences in outcomes as a function of the MGMT status of the tumors.
An important development with respect to tamoxifen has been the report (113) that it may be possible to predict which patients will benefit from tamoxifen. This Canadian study compared patients who responded to tamoxifen with those who did not and reported that there was a systematic difference in the metabolites of tamoxifen. This potentially allows for an early decision in treatment on whether to use tamoxifen.
The effectiveness of tamoxifen can be increased by suppressing thyroid function (114). Thyroid hormones maintain the level of insulin-like growth factor (IGF), which is now known to play an important role in causing resistance to various types of cancer treatments. Eleven of the 22 patients with recurrent tumors became hypothyroid following drug treatment. Their median survival time was 10.1 months, compared with 3.1 months for patients whose thyroid function had not been effectively suppressed. However, no information is available on how thyroid suppression affects survival time, regardless of the use of tamoxifen.
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Well, I hope you enjoyed reading, I have been as faithful as possible. Very soon the last part of the chapter!