Results from a Phase II Single Arm Trial Evaluating the Safety and Efficacy of Anhydrous Enol-Oxaloacetate on Improving Cognitive Complaints in Breast Cancer Survivors

Abstract

Background:

Cancer-related cognitive impairment (CRCI) affects a substantial proportion of breast cancer survivors (BCS) and effective pharmacologic interventions are lacking. Oxaloacetate (OAA), a naturally occurring metabolic intermediate with glutamate-scavenging, anti-inflammatory, and mitochondrial bioenergetic properties, was evaluated for its safety and preliminary efficacy in improving cognitive complaints in BCS with moderate to severe CRCI.

Methods:

We conducted a single-arm, phase II trial enrolling early-stage BCS who were 12 months to 5 years post–primary treatment and reported significant cognitive complaints on the PROMIS Cognitive Function questionnaire. Participants received oxaloacetate 500 mg orally twice daily for 8 weeks. The primary endpoint was improvement in perceived cognitive impairment, measured by the Functional Assessment of Cancer Therapy–Cognitive Function Perceived Cognitive Impairment (FACT-Cog PCI) score. Secondary outcomes included fatigue, insomnia, psychological symptoms, physical and mental health–related quality of life, neuropsychological test performance, and safety. Simon’s two-stage design with subsequent sequential monitoring was used.

Results:

Eighteen participants were enrolled; sixteen completed the intervention. All evaluable participants demonstrated clinically and statistically significant improvement in perceived cognitive impairment (mean FACT-Cog PCI change +26.4 points; p<0.0001), with improvement from the impaired to the normative range. Statistically significant improvements were also observed in total fatigue (p<.0001), mental fatigue (p<.0001), and physical function (p=.0003), with a trend toward improvement in insomnia (p=.09). Neuropsychological testing showed improvements in executive function and processing speed. Oxaloacetate was generally well-tolerated; gastrointestinal symptoms were the most common adverse events, leading to treatment discontinuation in two participants. There were no serious adverse events.

Conclusions:

Oxaloacetate treatment led to significant improvements in perceived cognitive impairment, fatigue, and physical functioning among BCS with CRCI, with acceptable tolerability. These findings support further investigation in a randomized, placebo-controlled trial to confirm efficacy.

During the past two decades, cancer-related cognitive impairment (CRCI) has emerged as one of the most concerning potential complications of cancer treatment.^1-6 Breast cancer survivors (BCS) have been among the most frequently studied. Increased reports of post-treatment cognitive difficulties emerged in the 1990s with the expanded use of adjuvant chemotherapy in early-stage breast cancer patients. This included the popular CMF (cyclophosphamide, methotrexate, 5FU) chemotherapy regimen containing two agents that cross the blood brain barrier with known direct neurotoxicity.⁷ As high dose adjuvant chemotherapy regimens were adopted in breast cancer treatment, patient reports of cognitive difficulties increased, with the earliest published CRCI reports suggesting a direct relationship between the intensity of chemotherapy treatment and cognitive dysfunction.^8,9

Subsequent clinical investigations followed, revealing the complexity of compromised cognition among BCS.^10-20 Cross-sectional and prospective neuroimaging studies suggested likely compromised substrates and networks.^21-28 Two meta-analyses examining post-treatment BCS identified significant deficits in neurocognitive test performance in several domains.^29,30 A large longitudinal study of breast cancer patients from community oncology clinics revealed significantly greater cognitive complaints both prior to and following chemotherapy treatment, compared to age-matched concurrent controls.²⁰ In addition to chemotherapy exposure, the majority of BCS receive prolonged adjuvant endocrine therapies (e.g., tamoxifen, aromatase inhibitors, ovarian function suppression) after initial treatment. Recent studies suggest that endocrine therapies either alone or in combination with adjuvant chemotherapy also contribute to CRCI,^31-34 but this issue has had less evaluation.^12,35-37

There is general consensus that CRCI is a biological consequence of cancer and its treatments; however, the mechanisms are thought to be multifactorial, reflecting predisposing patient characteristics (i.e., age, genetics, comorbid conditions, intellectual/cognitive reserve, education), cancer risk factors (e.g., DNA damage, toxic exposures, hormones, aging), lifestyle and behavioral factors (e.g., tobacco use, physical inactivity, alcohol use), and the effects of cancer treatment (e.g., direct drug toxicity, microvascular changes, systemic inflammation, free radicals, lowered estrogen levels).^38-41 Importantly, CRCI occurs in the setting of psychosocial and behavioral risk factors such as elevated anxiety and depression; indeed, the role of psychosocial factors in the development of CRCI is well-documented^42,43 and widely acknowledged in CRCI models.^44-46 A number of behavioral interventions have been evaluated and have shown some efficacy in helping patients manage CRCI.⁴⁷ Pharmacological interventions have also been assessed including stimulants (methylphenidate, modafinil), as well as drugs used in Alzheimer’s Disease (donepezil, memantine), but they have shown limited efficacy in small samples, and one large randomized placebo-controlled trial of donepezil in breast cancer patients was negative.⁴⁸ A recent review of the NIH portfolio of research on CRCI concluded that there are “unmet needs and opportunities to advance mechanistic and interventional research that supports cognitive health and quality of life for all cancer survivors.”⁴⁹ In particular, we focus on the need and opportunity to evaluate novel therapeutic strategies for this subgroup of 15-25% of BCS vulnerable to persistent cognitive dysfunction following breast cancer and its treatment.^1,41

Oxaloacetate (oxaloacetic acid when dry) is a human metabolite central to energy production within the cell and is involved in many important metabolic reactions. Oxaloacetate (OAA) is a key factor in the reversible enzymatic reaction that regulates glutamate by converting it to α-ketoglutarate. The mechanism by which OAA exerts an effect on the brain is indirect, involving the dynamics of glutamate metabolism. Berl et al.⁵⁰ described the existence of the blood-to-brain efflux of glutamate. The result of scavenging glutamate from the peripheral blood results in an increased efflux of brain glutamate into the blood.⁵⁰ Extensive research has been done with OAA as a glutamate scavenger in peripheral blood.^50-59

How is this relevant to CRCI? Local and systemic inflammation associated with chemotherapy and radiation likely trigger a central nervous system neuroinflammatory response that leads to associated neurobehavioral symptoms.^60,61 This neuroinflammatory response can result in acute and long-term excess extracellular glutamate, which can ultimately lead to excitotoxicity, downregulation of normal glutamatergic signaling, and apoptosis.⁶² Rönnbäck and Hansson⁶³ have hypothesized that proinflammatory cytokines could be involved in the pathophysiology of mental fatigue through their ability to attenuate the astroglial clearance of extracellular glutamate, their disintegration of the blood brain barrier, and effects on astroglial metabolism and metabolic supply for the neurons, leading to attenuation of glutamate signaling.⁶⁴ As OAA is a glutamate scavenger, there is a potential role for its action in moderating the effects of glutamate-related excitotoxicity resulting from neuroinflammation.

In pre-clinical work examining the potential effects of OAA on cerebral function, there has also been a focus on its role in influencing mitochondrial metabolism and energy production. Since abnormal brain bioenergetic function may contribute to neurodysfunction and neurodegeneration in Alzheimer’s disease (AD), manipulating brain bioenergetics may affect the symptoms or alter the course of AD. Mitochondrial dysfunction has also been proposed as a potential mechanism for CRCI.⁶⁵ A nutritional supplement form of OAA (anhydrous enol-oxaloacetate; MetVital, Inc.) had been tested for safety in two separate trials of older adults with AD and Parkinsons Disease, with minimal evidence of toxicity.^57,58,66 Given the paucity of pharmacological strategies to alleviate CRCI symptoms, we decided to assess OAA for potential benefit and safety among BCS with moderately severe CRCI symptoms, using a single arm, phase II trial design.

Methods

Subjects and Eligibility.

BCS were recruited from the Los Angeles community and the UCLA Health System with outreach to breast oncology clinicians. Research staff screened potential study participants by telephone assessing medical eligibility, and screening for severity of cognitive complaints using the PROMIS Adult v2.0-Cognitive Function 4a questionnaire, whose raw scores range from 4 to 20, with higher scores being better function.⁶⁷ For this study, a raw score of <12 was used to determine evidence of impairment as scores at this level represent the lowest 16^th percentile in women. ⁶⁸ Eligibility included: 1) Women with a diagnosis of early stage breast cancer (Stage 0, I, II, IIIa) who were at least 12 months after primary treatment (surgery, chemotherapy, radiation), but could be on endocrine therapy or HER-2 targeted therapy, and not more than 5 years after breast cancer diagnosis; 2) No evidence of active/recurrent breast cancer or other serious chronic illness; 3) Significant cognitive complaints, defined as a raw score of <12 on the PROMIS cognitive function measure. 4) Geographically accessible for in person evaluations, and able to participate in a study of 8-10 weeks duration; 5) age > 18 years and < 75 years; 6) ability to complete evaluation surveys in English; 7) If premenopausal, must agree to use adequate contraception; 8) Ability to understand and willingness to sign a written informed consent document. Screen-eligible BCS interested in study participation met with the study investigator by telephone to provide more detailed information about the study and review any concurrent medical problems that might interfere with eligibility. Following this review, they were scheduled for an in person visit to obtain study consent and conduct the pre-treatment clinical evaluation prior to starting the study medication. The study protocol was approved by the UCLA institutional review board, and was also approved by the FDA and an IND with the first author as the study sponsor. This investigator-initiated trial was monitored by the Data Safety Monitoring Board of the UCLA Jonsson Comprehensive Cancer Center, and was registered at ClinicalTrials.gov (Identifier: NCT04290897). The study protocol is available with this manuscript.

Procedures and Treatment.

The study schema is shown in Figure 1. After obtaining written informed consent, physical examination, electrocardiogram, and laboratory tests (CBC, differential, platelets, comprehensive chemistry panel) were performed at study baseline visit and subsequently at the end of treatment 8 weeks later. Pregnancy testing was performed in women who could potentially become pregnant. Participants completed a symptom checklist of items selected from the PRO-CTCAE⁶⁹ to assess (gastrointestinal symptoms, pain, fatigue, insomnia, headache) prior to starting the study medication to facilitate subsequent grading of the CTCAE version 4.0 adverse events after receipt of the study medication. The same PRO-CTCAE items were assessed at 4- and 8-weeks to facilitate grading of adverse events.

Figure 1.

Study schema

At baseline, 4-weeks and 8-weeks after starting the study medication, participants completed an electronic questionnaire battery to capture the most relevant biobehavioral outcomes of treatment with a minimum amount of participant burden (Supplement table 1). The primary study endpoint was the FACT-Cog Perceived Cognitive Impairment (FACT-Cog PCI)^70-72 score that has been shown in multiple studies to be a reliable, valid, and responsive measure of CRCI. The FACT-Cog PCI contains 18 items and asks about perceived cognitive impairment over the past 7 days, such as “I have had trouble concentrating,” with scores ranging from 0-72, with higher score being better. We previously demonstrated a cutpoint score of 54 for impairment derived from a normative sample data.⁷² The battery also used standardized measures to assess fatigue, sleep disturbance, depression, anxiety, as these behavioral symptoms are associated with CRCI in BCS. ^6,73-76 We also measured health-related quality of life using the SF-12 Physical and Mental Component Scales.⁷⁷

Most of the neurocognitive testing was performed over a HIPAA compliant and institutionally approved telehealth platform using remote administration procedures consistent with standard neuropsychological clinical practice. One computerized test was performed in clinic during the in-person study visits. Testing was performed after the baseline visit but before drug administration, and in the week prior to the 8-week study visit. We included standardized neuropsychological tests, focusing on those domains most relevant to CRCI - attention, processing speed, executive function, and memory (see Supplement table 2).⁷⁸ Test selection was informed by the International Cancer and Cognition Task Force guidelines,⁷⁹ and included a memory test with alternate forms available to protect against practice effects.⁸⁰ Neuropsychological measures are important secondary outcomes to examine treatment effects using standard clinical tools common across research and clinical settings. The entire battery took approximately 60 minutes and was administered by a neuropsychologist-trained research assistant who performed all tests during the trial.

Study Medication.

Participants received anhydrous enol-oxaloacetate 500 mg capsules by mouth twice a day. The medication was provided by MetVital, Inc. and was planned for an 8-week treatment period. Pill counts were performed at 4 and 8 weeks to assess adherence.

Safety Monitoring for Adverse Events.

Participants were contacted by the study coordinator weekly during the first two weeks after starting the study medication and were evaluated by the study investigator remotely at 4-weeks and again at the in-person assessment at 8-weeks, after which the medication was discontinued. Four weeks later, participants were contacted by the study coordinator to assess any residual toxicity. Clinical AEs were recorded at 4-, 8-and 12-week assessments by the study investigator.

Statistical Considerations.

The primary endpoint was a positive response, defined as an improvement in FACT-Cog PCI score of at least 4 points from baseline to the 8-week assessment. The original trial design was a Simon’s two-stage optimal design,⁸¹ computed using the R package clinfun.⁸² We specified 80% power and two-sided alpha of 0.05. The null response rate was specified as 0.25 based on symptom trials among breast cancer patients indicating that a typical placebo response rate is about 25%.⁸³ The response rate under treatment was specified as 0.50, i.e., twice the placebo response rate. With these parameters, the Simon’s optimal design was (r1/n1, r/n) = (2/9, 9/24): in stage 1, 9 participants are enrolled and treated. If 2 or fewer participants respond, the trial is terminated for lack of efficacy. Otherwise, the trial will continue until a total of 24 participants are enrolled and treated. If the total number of responders is 9 or fewer, it is concluded that the treatment lacks sufficient efficacy to warrant further investigation. If the number of responders is 10 or more, the treatment is considered for further investigation.

Interim analysis:

In June 2023, the interim analysis indicated an improvement of over 4 points in FACT-Cog PCI scores among all 9 initially treated participants (mean improvement 27.7 points, SD 12.5, range 18-56). Given the very large improvements observed across all participants, it was deemed appropriate to redesign the trial to have an additional interim analysis to allow for possibility of early termination for efficacy. We retained the original specifications of 80% power, two-sided alpha of 0.05 (operationalized as one-sided alpha of 0.025), and null response rate of 0.25, considered operating characteristics under true response rates of 0.50-0.70, and used these to construct a Pocock sequential design with three interim looks for efficacy after 9, 18 and 27 participants. Analyses at each look used exact binomial tests with local one-sided significance level 0.0110. The design was computed using the R package rpact (https://www.rpact.org/).

Results

Study Participants.

Between March 1, 2022, and May 28, 2024, 18 BCS were enrolled. We screened 57 BCS for eligibility: 20 were not eligible and 19 were eligible but declined to participate. Participant characteristics are shown in Table 1. The sample was ethnically diverse with mean age 49.6 years. Most had received adjuvant chemotherapy and 89% were currently receiving endocrine therapy. On average, they were 2.3 years since cancer diagnosis. Medical conditions reflected those common in mid-life women. Sixteen of the 18 participants completed the 8 weeks of study medication. The characteristics of the two women who discontinued treatment were like the 16 who completed the study. One participant discontinued the study medication after experiencing severe diarrhea during the first week of treatment and did not want to be rechallenged at a lower dose. A second participant had pre-existing gastrointestinal symptoms associated with abemaciclib (primarily dyspepsia and diarrhea) that were exacerbated; she was withdrawn by the study investigator after 2 weeks on study medication. Longitudinal follow-up data are available for 16 of the 18 participants and adverse events for all 18 enrolled participants.

Table 1.

Demographic and Medical Characteristics of Participants at Baseline Assessment (N = 18)

Demographic	All enrolled participants N=18	Evaluable participants N=16	Participants who discontinued N=2
Age
Mean (std dev)	49.6 (9.3)	49.8 (9.9)	48.4 (3.2)
Minimum	35.6	35.6	46.2
Maximum	75.0	75.0	50.7
Race
Asian	4 (22%)	3 (19%)	1 (50%)
White	12 (67%)	11 (69%)	1 (50%)
Biracial	1 (6%)	1 (6%)	0 (0%)
Prefer not to answer	1 (6%)	1 (6%)	0 (0%)
Ethnicity
Hispanic or Latino	1 (6%)	1 (6%)	0 (0%)
Not Hispanic or Latino	17 (94%)	15 (94%)	2 (100%)
Past Chemotherapy Yes	11 (61%)	10 (63%)	1 (50%)
No	7 (39%)	6 (37%)	1 (50%)
Current Endocrine Therapy
Yes	16 (89%)	14 (88%)	2 (100%)
No	2 (11%)	2 (12%)	0 (0%)
Years Since Diagnosis
Mean (std dev)	2.3 (0.8)	2.3 (0.8)	2.9 (1.1)
Minimum	1.3	1.3	2.1
Maximum	3.8	3.8	3.8
Years Since Last Treatment
Mean (std dev)	1.6 (0.9)	1.7 (0.9)	1.5 (n/a*)
Minimum	0.5	0.5	*No data for one of the two
Maximum	3.3	3.3
Stage
0	1 (6%)	1 (6%)	0 (0%)
1	9 (50%)	9 (56%)	0 (0%)
2	3 (17%)	1 (6%)	2 (100%)
3	1 (6%)	1 (6%)	0 (0%)
Not assessable*	4 (22%)	4 (25%)	0 (0%)
Surgery Type
Lumpectomy	8 (44%)	7 (44%)	1 (50%)
Mastectomy without reconstruction	1 (6%)	1 (6%)	0 (0%)
Mastectomy with reconstruction	8 (44%)	7 (44%)	1 (50%)
Other (lumpectomy + bilateral implants)	1 (6%)	1 (6%)	0 (0%)
Radiation
Yes	13 (72%)	12 (75%)	1 (50%)
No	5 (28%)	4 (25%)	1 (50%)
Medical Conditions
Heart disease	4 (22%)	4 (25%)	0 (0%)
GERD	6 (33%	6 (38%)	0 (0%)
Anemia or other blood disease	2 (11%)	2 (13%)	0.(0%)
Bone loss or osteoporosis	6 (11%)	5 (31%)	1 (50%)
Thyroid disease	2 (11%)	2 (13%)	0 (0%)
Allergies	1 (6%)	1 (6%)	0 (0%)
Asthma	2 (11%)	2 (13%)	0 (0%)
Frequent headaches/migraines	4 (22%)	3 (19%)	1 (50%)
PROMIS Adult v2.0 - Cognitive Function 4a administered at time of screening (lower score means more cognitive problems; score <12 needed for study eligibility)	Mean 8.3	Mean 8.4	Mean 7.5
	Std Dev 2.4	Std Dev 2.4	Std Dev 3.5
	Range 4-11	Range 4-11	Range 5-10

^*Received neoadjuvant chemotherapy

Primary Outcome Results.

The study met its primary outcome of significant improvement in perceived cognitive impairment measured by the FACT-Cog PCI over the 8 weeks of treatment (Figure 2), with all 16 of the assessable participants demonstrating significant improvement (p<0.0001). The mean change score among these participants was 26.4 points (SD 13.8, 95% CI 10.9, 33.8) (Table 2), with FACT-Cog PCI scores at baseline that were below the 54 score cutpoint for impairment, with a mean score of 29.1 SD 13.9. ⁷² By the end of treatment, the mean for the group was above 55.5 with SD 10.2. Supplementary Figure 1 includes the individual patient trajectories of FACT-Cog PCI over the 8 weeks of treatment. There was gradual improvement at 4 weeks with greater improvement in almost all participants by 8 weeks.

Figure 2.

FACT-Cog PCI scores over 8 weeks of oxaloacetate therapy. T1= baseline, pre-treatment, T2=4-week assessment, T3= 8-week assessment. Boxplots depict mean (X), median (middle line), 1st and 3rd quartiles (bottom and top edges of box) and minimum and maximum values (endpoints of whiskers). Mean change score, p<0.0001

Table 2.

Change scores for selected scales from T1 to T3

Scale	Mean change*	Std Dev	95% CI	p-value
FACT-Cog PCI with 18-items	26.4	13.8	(19.0, 33.8)	<.0001
SF-12
PCS	7.9	6.6	(4.3, 11.4)	.0003
MCS	3.2	9.2	(−1.7, 8.1)	.18
ISI	2.0	4.4	(−0.3, 4.3)	.09
MFSI
General	9.2	6.9	(5.5, 12.9)	<.0001
Physical	3.3	2.8	(1.8, 4.8)	.0003
Emotional	2.8	4.0	(0.7, 4.9)	.01
Mental	9.6	6.3	(6.3, 13.0)	<.0001
Vigor	3.7	1.0	(1.7, 5.8)	.002
Total	28.7	19.5	(18.3, 39.1)	<.0001
PROMIS T-scores
Depression	2.1	6.2	(−1.2, 5.3)	.20
Anxiety	3.5	8.3	(−0.9, 8.0)	.11

^*Change scores were scored such that a positive number means improvement, regardless of scale direction

Secondary Outcomes.

Other behavioral symptoms also improved on the oxaloacetate therapy (Table 2). The Multidimensional Fatigue Symptom Inventory (MFSI) total and subscale scores all showed significant improvement (P<.0001) over the 8 weeks of the trial. The Mental Fatigue subscale has been validated with another measure of CRCI in breast cancer and lymphoma patients. ⁸⁴ Significant improvement in the Mental Fatigue subscale provides additional support for the FACT-Cog PCI results. Physical functioning as measured by the SF-12 Physical Component Score (PCS) showed dramatic improvement over the course of the trial with a mean change score greater than a standard deviation (p=0.0003). The Mental Component Score (MCS) was in the normal range prior to treatment and did not change over the 8-week treatment period (p=0.18).

The Insomnia Severity Index (ISI) was also elevated at study entry and improved somewhat over the 8 weeks of the study (p=0.09). Neither the PROMIS Anxiety nor the PROMIS Depression scores were elevated in participants at study entry, and scores did not change significantly over time (both ps > 0.10).

Neurocognitive testing results.

Repeated measures ANOVA revealed several significant improvements in neuropsychological testing, particularly on measures of executive functioning and processing speed (see Table 3). These findings are considered exploratory given the small sample size and multiple comparison tests. However, it is notable to see improvements in these standardized tests with the OAA treatment, as a hallmark of CRCI is a failure to have improvements on repeat testing.

Table 3:

Results of Neuropsychological Tests in 16 participants

	Baseline T1		8 weeks T3		p value
	Mean	SD	Mean	SD
WAIS-IV Digit Span	10.19	1.68	11.81	2.76	0.008
HVLT R Total	49.44	11.30	53.63	10.93	0.08
HVLT-R Delayed Recall	48.75	9.34	51.88	9.54	0.09
DKEFS Color Word - Color Naming	9.69	2.58	10.69	1.85	0.048
DKEFS Color Word - Word Reading	9.94	2.24	10.75	2.49	0.2
DEKFS Color Word - Inhibition	10.94	2.89	12.50	2.13	<.01
DKEFS Color Word - Inhibition/Switching	10.88	2.92	12.19	2.01	<.01
DKEFS Letter Fluency	11.31	4.51	12.63	3.95	0.06
DKEFS Category Fluency	12.75	3.70	13.56	3.95	0.33
DKEFS Category Switching Total	13.81	3.95	13.44	3.63	0.56

Raw Scores Reported. WAIS-IV=Wechsler Adult Intelligence Scale, Fourth Edition; HVLT-R=Hopkins Verbal Learning Test, Revised; DEKFS=Delis Kaplan Executive Function System

Medication adherence.

Pill counts were available for 16 of the 18 who completed the study. Treatment days ranged from 46-64, with a mean of 56 days. Adherence (percent of expected pills taken) ranged from 62% to 100%, with a mean of 93%. Six participants had 100% adherence. The 62% adherence occurred in a participant who had difficulty remembering to take the medication twice a day.

Toxicity Monitoring and Adverse Events.

There were no significant changes in physical examination, electrocardiogram, or laboratory studies among the study participants. Table 4 shows all possibly related adverse events for the 18 enrolled participants. Overall, anhydrous enol-oxaloacetate 500 mg by mouth twice a day was well-tolerated with some mild gastrointestinal symptoms, most prominent being dyspepsia, bloating, constipation, diarrhea, and nausea. Many participants had GERD at study entry, and this was exacerbated in some participants. The two participants who discontinued the study early had gastrointestinal toxicity as described earlier. Symptoms experienced by the 16 participants who completed 8 weeks of treatment resolved in the 4-week follow-up after discontinuation of the medication.

Table 4.

AE Table - Related to Study Participation or Study Drug^*

AE Description	Grade					Total number of events across all grades	Percent of subjects that experienced AE across all grades
	1	2	3	4	5
Abdominal pain	2	1	0	0	0	3	16.7%
Bloatinq	4	0	0	0	0	4	22.2%
Constipation	5	0	0	0	0	5	27.8%
Diarrhea	1	1	0	0	0	2	11.1%
Dyspepsia	7	0	0	0	0	7	38.9%
Fatigue	1	0	0	0	0	1	5.6%
Flatulence	1	0	0	0	0	1	5.6%
Insomnia	1	0	0	0	0	1	5.6%
Nausea	3	0	0	0	0	3	16.7%
Rash	1	0	0	0	0	1	5.6%

^*Includes related events: possibly, probably and definitely for all 18 participants

Discussion

BCS with CRCI participating in this phase II study of anhydrous enol-oxaloacetate demonstrated significant improvements in cognition, fatigue, and physical functioning, using validated measures of patient reported outcomes to assess clinical benefit. Toxicity was primarily related to gastrointestinal symptoms. Eligibility screening for CRCI successfully identified study participants with severe cognitive difficulties compared to healthy population norms. Specifically, the mean participant raw score on the PROMIS Cognitive Function 4-item questionnaire was 8.3 which is a standardized T score of 34 (1.6 SD below the population norm of 50). Similarly low scores were documented at baseline pre-treatment on the FACT-Cog PCI, the primary trial outcome measure, and scores on this measure improved significantly in all study participants, far exceeding what would have been expected from a placebo response. To further support the biological impact of the OAA, statistically significant improvements in fatigue and physical functioning were observed, with a trend for significant improvement in insomnia symptoms. These symptoms were not screened for but were co-occurring, as has been frequently observed in BCS with CRCI, and are also associated with systemic inflammation after cancer treatments.^85-87 While the primary study outcome was clinically meaningful improvement in cognitive complaints, we were pleased to see the concomitant improvements in fatigue and insomnia, both of which may contribute to CRCI. An unexpected finding was the large improvement in physical functioning, which could be a downstream effect of improvement in energy (lower fatigue).

As noted in the study protocol, we had planned to assess markers of inflammation and mitochondrial function in the study participants (added to the protocol after the interim assessment and study re-design). Unfortunately, we were only able to obtain paired research blood samples in 5 of 9 participants in the latter half of the study, which was too small a sample for meaningful evaluation.

Interpretation of study results without a placebo or comparative treatment group has limitations. Being aware of this concern, we approached the study with skepticism about the activity of the supplement, using the rigor of the initial two-stage design. However, the impressive and universal improvements in perceived cognitive impairment in the first 9 study participants encouraged us to redesign the study to be able to complete it with a smaller total sample size, and to hasten the development of a randomized, placebo-controlled trial. In addition, we have undertaken further evaluation of OAA in a preclinical mouse model to gain a better understanding of the mechanism of action, using a placebo-controlled design. A phase II placebo-controlled trial of this nutritional supplement in BCS with CRCI was recently approved by the FDA and we anticipate opening the trial in the fourth quarter of 2026. These results were critical for development of the future study in determining the most frequent toxicities in BCS, and especially the potential challenges in taking the OAA in the setting of gastrointestinal toxicity from some CDK4/6 inhibitors.

Context Summary:

• Key objective: Is the nutritional supplement anhydrous enol-oxaloacetate effective in reducing symptoms of cognitive impairment in breast cancer survivors?

• Knowledge generated: Among 16 of 18 study participants with severe cognitive impairment, the nutritional supplement was well-tolerated and there were statistically significant improvements in self-reported cognition, fatigue, and physical functioning, including significant improvements in neurocognitive test performance over an 8-week period. These findings support further testing of oxaloacetate in a randomized placebo-controlled trial.