Compound danshen dripping pills for diabetic retinopathy in patients with type 2 diabetes: A superiority, randomized controlled trial

Abstract

BACKGROUND

Compound danshen dripping pill (CDDP), an approved treatment for non-proliferative diabetic retinopathy (NPDR) in China, has demonstrated potential in both preclinical and clinical studies. However, its efficacy in NPDR has not been validated through large clinical trials.

AIM

To evaluate the therapeutic efficacy and safety of CDDP in NPDR.

METHODS

This randomized, placebo-controlled, double-blind, multicenter study included 484 NPDR patients across 16 centers in China from November 2013 to July 2017. Eligible NPDR patients were randomly assigned to the CDDP and placebo groups at a ratio of 3:1. The intervention lasted for 24 weeks. The primary outcome was the overall effective rate of fundus changes at 24 weeks, assessed through retinal microvascular status, the number of hemorrhages, and exudation area. Secondary outcomes included retinopathy severity, traditional Chinese medicine (TCM) symptoms, macular edema, and corrected visual acuity. The full analysis set (FAS) included all enrolled cases who were randomized and administered at least one study drug.

RESULTS

Of the 484 randomized participants, 483 (362 and 121 in the CDDP and placebo groups, respectively) were included in the FAS. At 24 weeks, the overall effective rate in the CDDP group was 77.07%, significantly higher than 53.72% found in the placebo group (P < 0.001). Results remained consistent after adjusting for central effects and baseline HbA1c. Additionally, CDDP outperformed placebo in improving retinal lesion severity, microaneurysms, hemorrhages, diabetic macular edema, and TCM symptoms. The frequencies of adverse events detected by laboratory tests did not significantly differ between the two groups.

CONCLUSION

CDDP significantly and effectively alleviates NPDR. Future research should focus on assessing long-term outcomes.

Key Words: Diabetic retinopathy; Compound danshen dripping pills; Clinical trial; Efficacy; Safety

Core Tip: Compound danshen dripping pill (CDDP), an approved treatment for non-proliferative diabetic retinopathy (DR) in China, has demonstrated potential in both preclinical and clinical studies. However, its efficacy for non-proliferative DR (NPDR) has not been validated through large-scale clinical trials. We conducted this randomized, placebo-controlled, double-blind, multicenter study to confirm the therapeutic efficacy and safety of CDDP in NPDR.

INTRODUCTION

Evidence indicates that compound danshen dripping pill (CDDP), known for its blood-activating and stasis-dispelling properties, confers vascular and neuroprotective benefits[1,2]. In China, CDDP is widely utilized for diabetic retinopathy (DR) and has obtained approval from the China National Medical Products Administration[3]. CDDP primarily contains Salvia miltiorrhiza, Panax notoginseng, and Borneol. Pharmacological research suggests that CDDP alleviates retinal cell disorders, reduces vascular permeability, protects ganglion cells, and downregulates inflammatory factors, thereby enhancing retinal microcirculation[1,4,5], illustrated in Figure 1.

Figure 1 The pharmacological mechanism of compound danshen dripping pill in the treatment in diabetic retinopathy. tPA: Tissue type plasminogen activator; PAI: Photoacoustic imaging; FIB: Fibrinogen; HsCRP: Hypersensitive c-reactive protein; MCP: Monocyte chemotactic protein; TNF-α: Tumor necrosis factor- alpha; TC: Total cholesterol; LDL-C: Low density lipoprotein cholesterol; GSH-Px: Glutathione peroxidase; MDA: Malondialdehyde.

Recent estimates indicated that around 103 million people are affected by DR, making it a leading cause of vision loss among working-age adults globally[6,7]. Thus, enhancing clinical prevention and treatment strategies for DR is vital. Currently, several treatment options, including corticosteroid administration, anti-vascular endothelial growth factor therapy, and laser photocoagulation, are available for proliferative DR (PDR) and vision-threatening DR[8,9]. However, many cases do not respond adequately to these interventions and continue to experience disease progression and vision loss. At the non-PDR (NPDR) stage, blocking or delaying disease progression can provide substantial clinical benefits. Although various drugs have emerged over the years, studies examining their efficacy have reported inconclusive data. For instance, a clinical trial evaluating aspirin at 650 mg in DR patients found no delay in disease progression[10], and candesartan interventions have also shown unsatisfactory results[11]. While calcium dobesilate may alleviate DR severity[12], long-term studies of sodium dobesilate have reported negative outcomes[13].

Our previous phase II clinical trial involving 223 NPDR patients preliminarily assessed the therapeutic efficacy and safety of CDDP in DR, identifying the optimal dosage. After 24 weeks of intervention, we confirmed the efficacy of CDDP, with the medium-dose (540 mg, three times daily) being most effective for NPDR[14]. This study aimed to conduct a randomized controlled trial using this optimal dose to confirm the therapeutic efficacy and safety of CDDP in NPDR.

MATERIALS AND METHODS

Study design

This multicenter, double-blind, randomized, placebo-controlled clinical trial (ClinicalTrials.gov Identifier: NCT02388984) was conducted in accordance with the Declaration of Helsinki[15], Good Clinical Practice guidelines, and Chinese regulations. It was approved by the Ethics Committee of Guang’anmen Hospital of the China Academy of Chinese Medical Sciences (Approval number: 2013EC059-01). Participants diagnosed with NPDR were recruited in 16 centers (supplement 1 in Supplementary material). All participants provided informed consent before enrollment, which began on November 15, 2013 and concluded on July 7, 2017.

This study employed a superiority design. Previous trials indicated a total effective rate for the medium CDDP dose of 95.92% at 24 weeks, compared to 58.18% in the placebo group (14). With an α value of 0.05, a two-sided test, and a power (1 - β) of 0.90, the required experimental-to-placebo group ratio was determined to be 3:1, leading to an estimated sample size of 39:13. To account for a 20% anticipated withdrawal rate and the effectiveness and safety of CDDP, the total sample size was increased to 480 cases, with 360 in the CDDP group and 120 in the placebo group.

Other details, including the background information of the study, the management system for trial medications, quality control and quality assurance, and other comprehensive aspects of the study design, are provided in supplement 2-protocol in Supplementary material.

Study population

Inclusion criteria: (1) Diagnosis of NPDR by traditional Chinese medicine (TCM) syndrome differentiation of qi stagnation and blood stasis; (2) Age between 30 and 70 years; and (3) Signed informed consent.

Exclusion criteria: (1) Persistent hyperglycemia with HbA1c > 8.0%; (2) Previous treatment with retinal laser photocoagulation; (3) Diagnosis of PDR in one or both eyes; (4) DR secondary to type 1 diabetes; (5) Coexisting conditions such as glaucoma, uveitis, ocular neuropathy, or severe cataract; (6) Severe systemic disease (e.g., cardiovascular, hepatic, renal, hematological, or psychiatric disorders); (7) Pregnancy (or intention to become pregnant) or lactation in women; (8) Allergies to certain medications; (9) Participation in another clinical trial within the last month; (10) Use of DR medications within the last week; and (11) Systolic blood pressure > 160 mmHg or diastolic blood pressure > 100 mmHg. Withdrawal criteria are detailed in supplement 2-protocol in Supplementary material.

Randomization, blinding, and intervention

An independent statistician, not involved in study design or data collection, conducted randomization and blinding. The stratified block randomization method was applied, with stratification by center and an appropriate block length selected. Participants were randomly assigned to two groups at a 3:1 ratio. Using the PROC PLAN procedure in the SAS statistical software and specifying a seed number, a random allocation schedule was generated for 480 cases, indicating the assigned treatment (trial or control drug) corresponding to serial numbers of 001-480 (i.e., the overall randomization code list). Participants, clinical investigators, and statisticians were blinded to treatment allocation, with unblinding occurring only after all data were recorded. The placebo matched CDDP in color, smell, appearance, and packaging to maintain blinding. Although this was a multicenter study, individual-level randomization with center stratification is recommended by CONSORT for multicenter superiority trials and is widely accepted. We therefore adopted block randomization stratified by center to ensure balance within each center, rather than cluster randomization, which increases design complexity and reduces statistical efficiency. The complete randomization code list and center-level allocation records are provided in supplement 1 in Supplementary material.

All researchers received comprehensive protocol training prior to the study. Patients were randomly assigned to receive CDDP (Tianjin Tasly Pharmaceutical Group Co., Ltd; Batch number: 120607) or placebo (Batch number: 20120601) for 24 weeks, at 540 mg three times daily. Supplement 2-protocol in Supplementary material provides the study schedule, which included random enrollment and the treatment period, with six follow-up visits scheduled every four weeks except in case of patient withdrawal, loss to follow-up, or death. Participants received both oral and written information about the study and provided signed informed consent. To ensure blinding rigor, the placebo was consistent with CDDP in color, taste, appearance, size, and labeling.

Outcomes

The primary outcome was the overall effective rate of fundus changes assessed at 24 weeks post-treatment, focusing on three dimensions: Retinal microvascular condition, number of hemorrhagic points, and exudation area. Fundus change evaluation criteria included four levels: Remarkable effect, effectiveness, stability, and worsening. The overall effective rate was calculated by dividing the number of participants with overall effectiveness (remarkable effect, effectiveness, and stability) by the total number of participants in the group. This efficacy standard was designed by a third-party evaluation group based on early treatment diabetic retinopathy study international standards, in consultation with the Wisconsin Fundus Evaluation Center in the United States Fundus photographs were graded by a team of professional reviewers to ensure a uniform, standardized evaluation and assessment. The third-party evaluation system established in this study mainly included the following tasks: Developing a standardized system for assessing primary efficacy indicators, establishing evaluation methods for fundus fluorescein angiography (FFA), establishing evaluation methods for fundus photographs, and formulating independent image reading procedures, personnel qualification requirements, quality control procedures, and standard operating procedures. Detailed evaluation standards and third-party evaluation documents are provided in supplement 3 in Supplementary material.

Overall Efficacy Rate of Comprehensive Evaluation of Fundus Changes at 24 weeks. Determination criteria involved combining fundus FFA and color fundus photographs (collecting relevant data on hemorrhage and effusion) to analyze the degree of retinal microangiopathy and measured values. Based on indicators such as microaneurysms, microvascular abnormalities, retinal venous beading, capillary non-perfusion areas, and neovascularization in the four quadrants of the fundus, an evaluation scale (FFA scale) was designed to assess each item individually. Efficacy was determined according to four levels: Marked effectiveness, effectiveness, stability, and worsening. Marked effectiveness was defined by the following criteria: Comprehensive assessment indicated a reduction in the degree of retinal microangiopathy, including improvement in evaluation points on the FFA scale, the number of hemorrhages (assessed through color fundus photographs), and the area of effusion (assessed through color fundus photographs). In the same baseline group, improvement in one or more indicators in the FFA scale or reduction in the number of hemorrhages (reaching a markedly reduced level, without worsening of effusion). Effectiveness was defined by a comprehensive assessment indicating improvement in the degree of retinal microangiopathy, including FFA scale points, the number of hemorrhages (assessed through color fundus photographs), and the area of effusion (assessed through color fundus photographs). In the same baseline group, improvement in one or more indicators in the FFA scale or reduction in the number of hemorrhages (reaching a level of reduction, without significant worsening of effusion). Stability was defined as not meeting the criteria for marked effectiveness, effectiveness, or worsening. Worsening was defined by worsening of retinal microangiopathy or proliferative changes such as retinal neovascularization; worsening in the FFA scale or an increase in the number of hemorrhages in the same baseline group (assessed through color fundus photographs), with reference to changes in the area of effusion (assessed through color fundus photographs). The detailed criteria for the four levels (marked effectiveness, effectiveness, stability, and worsening) are shown in Table 1.

Table 1 Detailed criteria for efficacy determination.

Grading	FFA scale	Hemorrhage	Effusion (reference)
Marked effectiveness	Improvement in at least one evaluation point	Reduced > 50%	Absent/stable/reduced
	Improvement in at least 2 evaluation points	Absent/stable	Absent/stable/reduced
Effectiveness	Improvement in at least one evaluation point	Reduced ≤ 50%	Absent/stable/reduced
	Improvement in at least one evaluation point	Absent/stable	Absent/stable/reduced
	Stable	Reduced < 50%	Absent/stable/reduced
	Stable	Stable	Reduced ≥ 50%
Stability	Patients not meeting the criteria for marked effectiveness, effectiveness, or worsening
Worsening	Occurrence of worsening in one or more evaluation points	Increased	Absent/stable/increased
	Occurrence of worsening in two or more evaluation points	Absent/stable	Absent/stable/increased
	Or occurrence of IRMA/neovascularization/venous beading
	Stable	Increased	Absent/stable/increased
	Stable	Stable	Increased ≥ 50%

FFA: Fundus fluorescein angiography; IRMA: Intraretinal microvascular abnormalities.

Secondary outcomes included changes in retinal lesion severity at 24 weeks (classified as alleviated, unchanged, or worsened), overall evaluation of TCM symptoms, presence of macular edema, corrected vision, assessments of fundus changes including FFA scale evaluation, fundus photography (FP) hemorrhage evaluation, and FP exudation evaluation. Specific definitions and evaluation criteria are detailed in supplement 2-protocol in Supplementary material. Safety outcomes included the incidence rates of adverse and serious adverse events (SAE).

Statistical analysis

Data cleaning and validation preceded all statistical analyses, conducted using SAS version 9.4 (SAS Institute Inc.), with a two-sided P < 0.05 considered statistically significant (supplement 4 in Supplementary material). This study analyzed the full analysis set (FAS), comprising all enrolled subjects who were randomized and administered at least one study drug. Missing efficacy indicators in the FAS were addressed using the last observation carried forward method based on the intention-to-treat principle. Quantitative indicators were presented as mean and SD, and categorical indicators as count and percentage. Comparisons were conducted by the Cochran-Mantel-Haenszel (CMH) χ² test to assess the total effective rate in the comprehensive evaluation of fundus changes, controlling for site effects. In case H0 was rejected at the α level or with the lower limit of the 95%CI for the difference in total effective rates between the two groups exceeding zero, the investigational group was considered to have superiority over the control group. The severity of retinopathy at each visit and changes in severity vs pretreatment between the two groups were compared by the CMH χ² test, controlling for site effects for ordinal data. Changes in microangiomas, hemorrhages, and hard exudates were compared by the paired t-test or the Wilcoxon signed-rank test. The presence of bead-like fundus neovascularization and diabetic macular edema (DME) at baseline and weeks 12 and 24 was assessed by the χ² test or the Fisher's exact probability method. Changes in intraretinal microvascular abnormalities were evaluated by the CMH χ² test. Visual acuity data were converted using the formula 5-log (1/decimal visual acuity) and recorded on a 5-point scale, analyzed similarly to microangiomas. The proportions of cases with TCM symptoms classified as ineffectiveness, improvement, or cure were compared by the CMH χ² test.

Safety were evaluated similarly to microangioma scores, with adverse events analyzed by the χ² test or the Fisher's exact test. Meanwhile, we conducted a stratified analysis using 60 years of age as a cutoff to assess the clinical safety of CDDP in patients over 60 years old.

Subgroup analysis

We performed subgroup analyses based on baseline NPDR severity (mild, moderate, severe), baseline blood glucose (HbA1c < 7%, HbA1c ≥ 7%), and duration of diabetes (< 5 years, ≥ 5 years). The subgroup analyses focused on efficacy outcomes, mainly including the overall efficacy rate, FFA scale evaluation, and FP hemorrhage evaluation. We performed safety subgroup analyses based on baseline ages (≥ 60 years vs < 60 years), expanded the description of adverse and SAE.

RESULTS

Between November 15, 2013 and July 7, 2017, a total of 702 participants were screened for eligibility, of whom 218 were excluded. Ultimately, 484 participants were randomly assigned to the CDDP (n = 363) and placebo (n = 121) groups. In the CDDP group, 362 participants were included in the FAS, vs 121 in the placebo group. Detailed results are illustrated in Figure 2.

Figure 2 Study flowchart. CDDP: Compound danshen dripping pill.

Baseline characteristics

The baseline characteristics of participants in the FAS are summarized in Table 2. Baseline data were comparable between the two groups (P > 0.05).

Table 2 Baseline characteristics and demographics of randomized patients, n (%).

	CDDP (n = 362)	Placebo (n = 121)	P value
Demographics
Gender (male/female)	192/170	59/62	0.415
Age (years)	58.22 (8.13)	57.22 (8.01)	0.196
Positive pregnancy test (women only)	0 (0.00)	0 (0.00)	0.971
Height (m)	1.65 (0.08)	1.65 (0.08)	0.733
Weight (kg)	65.86 (10.70)	65.85 (10.10)	0.877
BMI (kg/m2)	24.11 (2.93)	24.24 (2.94)	0.662
Treatment for diabetes
Duration of diabetes (years)	10.42 (5.90)	10.01 (6.07)	0.382
Sulfonylureas preparation	98 (27.84)	29 (24.58)	0.489
Biguanides preparation	148 (42.05)	49 (41.53)	0.921
Alpha-glucosidase inhibitor	116 (32.95)	33 (27.97)	0.314
Insulin	179 (50.85)	62 (52.54)	0.751
Other diabetes medications	48 (13.64)	12 (10.17)	0.329
HbA1c (%)	6.89 (0.95)	6.96 (0.92)	0.454
Duration of DR (years)	2.31 (2.85)	2.44 (3.06)	0.662
Retinopathy level in worst eye (ETDRS scale)			0.437
No obvious diabetic retinopathy	0 (0.00)	0 (0.00)
Mild NPDR	127 (35.08)	48 (39.67)
Moderate NPDR	182 (50.28)	56 (46.28)
Severe NPDR	53 (14.64)	17 (14.05)
PDR	0 (0.00)	0 (0.00)
General ophthalmologic examination
Left eye’s corrected vision (Snellen's test-chart)	4.71 (0.47)	4.76 (0.46)	0.099
Right eye’s corrected vision (Snellen's test-chart)	4.72 (0.47)	4.78 (0.40)	0.113
Fundus changes
Microaneurysms	362 (100)	121 (100)	> 0.999
Hemorrhage	115 (34.53)	44 (38.94)	0.398
Hard exudates	137 (41.14)	39 (34.51)	0.213
Microvascular abnormalities			0.178
No abnormality	306 (84.53)	102 (84.30)
Mild abnormality	31 (8.56)	7 (5.79)
Severe abnormality	25 (6.91)	12 (9.92)
Venous beading	6 (1.66)	2 (1.65)	> 0.999
Diabetic macular edema	59 (21.15)	19 (21.59)	0.929
Neovascularization	0 (0.00)	0 (0.00)	> 0.999

BMI: Body mass index; DR: Diabetic retinopathy; ETDRS: Early treatment diabetic retinopathy study; NPDR: Non-proliferative diabetic retinopathy; PDR: Proliferative diabetic retinopathy.

Primary outcome

The overall effective rate of fundus changes: After 24 weeks of treatment, the overall effective rate in the CDDP group was 77.07%, vs 53.72% in the placebo group, indicating a statistically significant difference (95%CI for the difference: 0.135 to 0.332, CMH = 25.051, P < 0.001). In the experimental group, the proportions of participants with remarkable, effective, and stable outcomes were 19.34%, 15.47%, and 42.27%, respectively, vs 3.31%, 13.22%, and 37.19% in the placebo group, respectively. Group comparison yielded a significant difference (CMH = 31.069, P < 0.001). A model analysis adjusted for center effect and baseline HbA1c levels confirmed these results, consistent with the unadjusted univariate logistic regression model (supplement 1 in Supplementary material).

Secondary outcomes

Changes in severity level of retinal microangiopathy: At 24 weeks, 21 cases (5.8%) in the CDDP group showed improvement in retinal microangiopathy, while 4 (1.1%) experienced exacerbation. In contrast, 4 cases (3.31%) in the placebo group displayed improvement, while 5 (4.13%) worsened. Additionally, 337 cases (93.09%) in the CDDP group vs 112 (92.56%) in the placebo group maintained stable retinal microangiopathy vs baseline. This difference was statistically significant (P = 0.040; Figure 3).

Figure 3 Changes in the severity of retinal microangiopathy. CDDP: Compound danshen dripping pill.

Changes in the FFA score of retinal microaneurysms: At week 24, mean (SD) changes from baseline in the FFA score of retinal microaneurysms were -0.31 (2.00) and +0.06 (1.49) in the CDDP and placebo groups, respectively, with a significant difference between the two groups (P = 0.036; supplement 1 in Supplementary material).

Changes in the FP score of retinal hemorrhage: At 24 weeks, the retinal hemorrhage score improved by -0.28 (1.11) in the CDDP group, while the placebo group showed a deterioration of +0.38 (1.68). The difference in score changes was significant (P < 0.001; supplement 1 in Supplementary material).

Change rates of retinal hard exudate area: At week 24, retinal exudate areas in the CDDP group decreased by 22% (median) from baseline, compared to a 10% decrease in the placebo group. However, the difference was not statistically significant (P = 0.419; supplement 1 in Supplementary material).

Changes in bead-like, intraretinal microvascular abnormality and fundus neovascularization: Evaluation of bead-like changes, intraretinal microvascular abnormalities, and fundus neovascularization showed no significant differences between the two groups at 24 weeks (P > 0.050; Table 3).

Table 3 Changes in bead-like, intraretinal microvascular abnormality and fundus neovascularization, n (%).

	CDDP (n = 362)	Placebo (n = 121)	P value
Bead-like
Baseline			> 0.999
None	356 (98.34)	119 (98.35)
Present	6 (1.66)	2 (1.65)
12 weeks			> 0.999
None	356 (98.34)	119 (98.35)
Present	6 (1.66)	2 (1.65)
24 weeks			> 0.999
None	356 (98.34)	119 (98.35)
Present	6 (1.66)	2 (1.65)
Intraretinal microvascular abnormalities
Baseline			0.578
No abnormality	306 (84.53)	102 (84.30)
Mild abnormality	31 (8.56)	7 (5.79)
Severe abnormality	25 (6.91)	12 (9.92)
12 weeks			0.716
No abnormality	305 (84.25)	104 (85.96)
Mild abnormality	32 (8.84)	5 (4.13)
Severe abnormality	25 (6.91)	12 (9.92)
24 weeks			0.394
No abnormality	305 (84.25)	100 (82.64)
Mild abnormality	30 (8.29)	9 (7.44)
Severe abnormality	27 (7.46)	12 (9.92)
Fundus neovascularization
Baseline
None	362 (100)	121 (100)
Present	0 (0.00)	0 (0.00)
12 weeks			0.999
None	360 (99.45)	120 (99.17)
Present	2 (0.55)	1 (0.83)
24 weeks			0.999
None	360 (99.45)	120 (99.17)
Present	2 (0.55)	1 (0.83)

CDDP: Compound danshen dripping pill.

Proportions of DME: At week 24, the number of patients with DME in the CDDP group decreased to 49 (17.07%), while the placebo group had an increase to 26 (27.08%). This difference was statistically significant (P = 0.032; supplement 1 in Supplementary material).

Changes in visual acuity: At week 24, the mean improvement in left eye visual acuity letter score from baseline was +0.05 (0.24) in the CDDP group, vs +0.02 (0.21) in the placebo group. The improvement in the CDDP group was significant compared to baseline (P < 0.001), though both groups showed similar values (P = 0.097; supplement 1 in Supplementary material). Similarly, the mean improvement in the right eye visual acuity letter score was +0.05 (0.25) in the CDDP group, vs +0.01 (0.19) in the placebo group, with a significant difference between the two groups (P = 0.036; supplement 1 in Supplementary material).

Changes in TCM symptoms: At 24 weeks, evaluation of single symptoms (dim vision, dull complexion, dry eyes, scaly dry skin, and limb numbness) showed significant improvements in dim vision, dull complexion, and dry eyes in the CDDP group vs the placebo group. However, changes in scaly dry skin and limb numbness did not significantly differ between the two groups. Supplement 1 in Supplementary material presents the changes in proportions of participants with ineffective, improved, and cured TCM symptoms.

Monitoring indicators: At each visit, including pre- and post-treatment, fasting blood glucose levels remained stable at approximately 8 mmol/L, with no significant differences between the two groups (supplement 1 in Supplementary material). HbA1c levels were consistently controlled at around 7% in both groups (supplement 1 in Supplementary material). Systolic blood pressure remained stable at approximately 125 mmHg, and diastolic pressure was close to 80 mmHg, without exceeding these values at any visit (supplement 1 in Supplementary material). Coagulation function remained normal throughout the study.

Safety

Adverse events: A total of 208 adverse events were reported in 128 patients, yielding an incidence rate of 26.50%. In the CDDP group, 143 adverse events occurred in 92 cases (25.41%), while 65 adverse events were reported in 36 cases of the placebo group (29.75%). No statistically significant difference in incidence rates was found between the two groups (P = 0.344; Table 4). Most adverse events were mild (Table 4).

Table 4 Rates of adverse events.

	CDDP group (n = 362)			Placebo group (n = 121)			P value
	Number of times	Number of cases	Percentage (%)	Number of times	Number of cases	Percentage (%)
Adverse events	143	92	25.41	65	36	29.75	0.344
Mild	108	73	20.17	50	32	26.45	0.162
Moderate	32	26	7.18	14	11	9.09	0.554
Severe	3	3	0.83	1	1	0.83	> 0.999
Serious adverse events	6	6	1.66	1	1	0.83	0.686
Adverse events occurring in at least 1% of participants in one or more groups
Infections	21	18	4.97	7	6	4.96	1.000
Urinary tract infection	6	6	1.66	4	4	3.31	0.278
Upper respiratory tract infection	8	7	1.93	1	1	0.83	0.686
Nervous system disorders	2	2	0.55	8	8	6.61	0.000
Dizziness	2	2	0.55	4	4	3.31	0.037
Blood and lymphatic system disorders	3	3	0.83	2	2	1.65	0.603
Coagulation disorder	3	3	0.83	2	2	1.65	0.603
Investigations	52	39	10.77	26	16	13.22	0.509
Increased gamma-glutamyl transferase	2	2	0.55	2	2	1.65	0.262
Positive urine leukocytes	5	5	1.38	8	6	4.96	0.033
Increased blood creatine phosphokinase	5	5	1.38	3	3	2.48	0.420
Increased blood creatinine	5	4	1.10	1	1	0.83	1.000
Decreased blood glucose	5	5	1.38	1	1	0.83	1.000
Increased blood glucose	9	8	2.21	1	1	0.83	0.461
Decreased platelet count	0	0	0.00	2	2	1.65	0.062

CDDP: Compound danshen dripping pill.

SAE: Seven cases experienced SAEs, suggesting an incidence rate of 1.45%. Six cases in the CDDP group experienced SAEs (1.66%), while one case in the placebo group had one SAE (0.83%, P = 0.686). All SAEs were deemed unrelated or possibly unrelated to the study drug, with detailed descriptions available in supplement 1 in Supplementary material. No serious adverse reactions or deaths occurred during the study.

Subgroup results: For the Overall Efficacy Rate outcome, in the NPDR severity subgroups, CDDP showed potentially better efficacy in the mild (P = 0.015) and moderate (P < 0.001) subgroups. In the HbA1c subgroups, there was no significant difference between the two groups. In the duration of diabetes subgroups, CDDP demonstrated potentially better efficacy in the ≥ 5 years subgroup (P < 0.001) (Table 5).

Table 5 Subgroup results of efficacy rate, n (%).

Overall efficacy rate	Subgroup	n (CDDP/placebo)	CDDP	Placebo	Between-group difference in overall efficacy rate (95%CI)	Test statistic (CMH)	P value
NPDR severity	Mild	127/48	101 (79.53)	30 (62.5)	0.016-0.324	5.899	0.015
	Moderate	182/56	139 (76.37)	27 (48.21)	0.076-0.341	15.655	< 0.001
	Severe	53/17	39 (73.58)	8 (47.06)	0.000-0.531	1.759	0.185
HbA1c	< 7%	197/64	158 (80.20)	38 (59.38)	0.076-0.341	15.155	< 0.001
	≥ 7%	163/55	121 (74.23)	26 (47.27)	0.122-0.418	12.202	< 0.001
Duration of diabetes	< 5 years	57/23	46 (80.70)	13 (56.52)	0.015-0.469	2.963	0.085
	≥ 5 years	305/98	233 (76.39)	52 (53.06)	0.124-0.343	18.615	< 0.001

NPDR: Non-proliferative diabetic retinopathy; CDDP: Compound danshen dripping pill; CMH: Cochran-Mantel-Haenszel.

For the FFA Scale Evaluation outcome, in the NPDR severity subgroups, CDDP showed potentially better efficacy only in the mild subgroup (P = 0.034). In the HbA1c subgroups, no obvious distinction was observed between the two groups. In the duration of diabetes subgroups, CDDP showed potentially better efficacy in the ≥ 5 years subgroup (P = 0.025) (Table 6).

Table 6 Subgroup results of fluorescein angiography scale evaluation, mean ± SD.

Fluorescein angiography scale evaluation	Subgroup	n (CDDP/placebo)	CDDP changes from 24 weeks to baseline	Placebo changes from 24 weeks to baseline	Within-group comparison statistic (Wilcoxon rank-sum test)	95%CI	P value
NPDR severity	Mild	127/48	-0.35 ± 1.63	0.00 ± 0.77	2.114	-0.83 to 0.14	0.034
	Moderate	182/56	-0.26 ± 1.98	0.02 ± 1.97	0.753	-0.87 to 0.32	0.451
	Severe	53/17	-0.40 ± 2.78	0.35 ± 1.22	0.779	-2.14 to 0.64	0.431
HbA1c	< 7%	197/64	-0.41 ± 1.97	0.00 ± 1.83	1.109	-0.96 to 0.14	0.267
	≥ 7%	163/55	-0.19 ± 2.04	0.09 ± 1.01	1.484	-0.85 to 0.28	0.138
Duration of diabetes	< 5 years	57/23	-0.49 ± 3.08	-0.22 ± 0.52	0.343	-1.57 to 1.02	0.727
	≥ 5 years	305/98	-0.28 ± 1.73	0.12 ± 1.63	2.239	-0.79 to -0.01	0.025

NPDR: Non-proliferative diabetic retinopathy; CDDP: Compound danshen dripping pill.

For the FP Hemorrhage Evaluation outcome, in the NPDR severity subgroups, no significant differences were observed among the three subgroups. In the HbA1c subgroups, CDDP showed potentially better efficacy in the ≥ 7% subgroup (P < 0.001). In the duration of diabetes subgroups, no significant differences were found between the two subgroups (Table 7).

Table 7 Subgroup results of fundus photography hemorrhage evaluation, mean ± SD.

Fundus photography hemorrhage evaluation	Subgroup	n (CDDP/placebo)	CDDP changes from 24 weeks to baseline	Placebo changes from 24 weeks to baseline	Within-group comparison statistic (Wilcoxon rank-sum test)	95%CI	P value
NPDR severity	Mild	127/48	0.01 ± 0.09	0.13 ± 0.46	2.673	-0.21 to -0.04	0.007
	Moderate	182/56	-0.40 ± 1.34	0.57 ± 2.20	3.581	-1.46 to -0.49	< 0.001
	Severe	53/17	-0.63 ± 1.46	0.43 ± 1.83	0.211	-2.05 to -0.06	0.004
HbA1c	< 7%	197/64	-0.27 ± 1.04	-0.05 ± 1.28	1.448	-0.54 to 0.10	0.147
	≥ 7%	163/55	-0.31 ± 1.20	0.88 ± 1.97	5.717	-1.65 to -0.73	< 0.001
Duration of diabetes	< 5 years	57/23	-0.51 ± 1.36	-0.14 ± 1.42	2.106	-1.07 to 0.32	0.035
	≥ 5 years	305/98	-0.23 ± 1.05	0.51 ± 1.72	4.884	-1.04 to -0.44	< 0.001

NPDR: Non-proliferative diabetic retinopathy; CDDP: Compound danshen dripping pill.

In the stratified analysis, compared to the placebo, CDDP did not significantly increase the incidence rates of adverse events, SAE, and withdrawals due to adverse events, regardless of whether patients were younger than 60 years or aged 60 years and above (Table 8).

Table 8 Subgroup results of safety³.

	CDDP			Placebo			P value
	Cases	n	%2	Cases	n	%2
Adverse event1	143	92	25.41	65	36	29.75	0.344
< 60 (year)	70	49	25.93	36	23	34.33	0.207
≥ 60 (year)	73	43	24.86	29	13	24.07	1.000
Serious adverse events	6	6	1.66	1	1	0.83	0.686
< 60 (year)	3	3	1.59	1	1	1.49	1.000
≥ 60 (year)	3	3	1.73	0	0	0.00	1.000
Withdrawn due to adverse events	7	7	1.93	2	1	0.83	0.686
< 60 (year)	4	4	2.12	2	1	1.49	1.000
≥ 60 (year)	3	3	1.73	0	0	0.00	1.000

¹Adverse reactions refer to three types of reactions that are positively related, possibly related, or undetermined to the investigational drug.

²Percentage = number of safety incidents occurring in each group and layer/total number of subjects in each group and layer.

³The total number of safety set participants in the experimental group was 362 (189 for those under 60 years old and 173 for those over 60 years old); The total number of safety set participants in the control group was 121 (67 for those under 60 years old and 54 for those over 60 years old).

CDDP: Compound danshen dripping pill.

DISCUSSION

Patients with PDR display severe retinal lesions and significant vision loss, which is often irreversible. Thus, intervening at the NPDR stage may be beneficial, potentially slowing disease progression and reducing future disabilities. Extensive clinical studies, including the Diabetes Control and Complications Trial[16], Action to Control Cardiovascular Risk in Diabetes[17], United Kingdom Prospective Diabetes Study[18] and Fenofibrate Intervention and Event Lowering in Diabetes[19] have shown that strict control of blood glucose and lipids can reduce the risk of DR occurrence and progression. However, long-term adherence to strict glucose control can be challenging and may increase the risk of hypoglycemic episodes. Early treatment studies indicated that retinal photocoagulation can lower the risk of vision loss in patients with clinically significant macular edema[20], although it does not significantly benefit mild to moderate NPDR.

This randomized, double-blind, multicenter clinical study assessed the therapeutic efficacy and safety of an optimal dosage of CDDP in NPDR. Over a 24-week treatment period, the overall effective rate (measured by changes in retinal microvascular conditions based on the FFA scale, number of hemorrhagic points, and area of exudation) was significantly better in the CDDP group than in the placebo group, corroborating our Phase II clinical study findings. The CDDP group showed greater improvements in retinal microvascular lesions, with only 1.1% of cases experiencing progression and 6% showing improvement by week 24. This suggests that CDDP may effectively prevent DR progression, with effects improving from week 12 to week 24, indicating potential long-term efficacy. For the subgroup analysis, the results indicated that patients in the mild NPDR severity subgroup and those in the duration of diabetes ≥ 5 years subgroup may experience more pronounced therapeutic benefits, mainly reflected in the overall efficacy rate outcome. Of course, these findings are based on subgroup analyses rather than definitive conclusions, but they provide a foundation for identifying the populations that may benefit most from treatment in future studies.

Post-marketing surveillance data of CDDP have shown that CDDP may cause symptoms related to the nervous system, e.g., dizziness, but there is no direct evidence indicating an increased risk of urinary system abnormalities. In this study, the incidence rates of urinary system abnormalities and dizziness were lower in the treatment group than in the placebo group. This discrepant result may be due to the fact that both dizziness and urinary abnormalities are low-probability events, and the observed difference could be incidental. In future studies, we will conduct more clinical research to further evaluate the safety of CDDP.

Microaneurysms and hemorrhages are initial manifestations of DR that often progress, frequently leading to macular edema[21,22]. The current study found significant reductions in microaneurysms and retinal hemorrhages in the CDDP group, suggesting a protective effect against macular edema. Among the 59 patients diagnosed with macular edema before treatment in the CDDP group, 16.9% experienced symptom resolution, further supporting the drug's efficacy on fundus lesions.

Additionally, the patients examined in this study showed TCM patterns of Qi stagnation and blood stasis, exhibiting symptoms such as blurred vision, dryness, and numbness. After 24 weeks of treatment, improvements were noted in blurred vision, overall complications, and dry eyes.

Given that cases were primarily at the NPDR stage, fundus lesions had a minimal impact on vision. At baseline, the visual acuity score averaged 4.7, and while the CDDP group showed a higher score post-treatment, the difference between the two groups was not statistically significant. Few participants reported symptoms related to bead-like changes, microvascular abnormalities, and capillary non-perfusion areas, with no significant differences observed. Consistent with previous safety data, no SAE were recorded during this trial.

The potential mechanisms by which CDDP alleviates NPDR mainly involve reduction of microaneurysms and hemorrhages, which may be attributed primarily to its anti-inflammatory effects and direct vascular protection. One animal study evaluated the potential mechanisms of CDDP in preventing early DR and found that its protective effects were mainly associated with decreased vascular permeability and reduced levels of inflammatory factors in retina and serum[1]. Another animal study also demonstrated that CDDP could alleviate retinal vascular leakage in DR models, which might be related to increased retinal pigment epithelium thickness and decreased levels of pro-inflammatory factors, including tumor necrosis factor-α and interleukin-6[2].

Limitations

Several limitations warrant consideration. First, CDDP is a compound TCM derived from various plants. While this trial showed clinical benefits, the active ingredients and mechanisms of action remain unidentified. Second, while CDDP may decrease DME, the current study did not account for changes in macular retinal thickness and/or edema severity, which deserve further investigation. Third, when applying these results clinically, the used eligibility criteria, e.g., visual acuity and severity of retinal microvascular lesions, must be considered, as findings may not be applicable to individuals with PDR or those needing retinal photocoagulation.

Of course, we must also acknowledge that in this study, after 24 weeks of intervention, CDDP was already shown to effectively improve NPDR. With a longer intervention period, additional benefits might be observed, including improvement in visual acuity and a reduced likelihood of NPDR progressing to PDR.

In this study, we indeed recognize that improvements in retinal lesions, macular edema, and visual acuity were not entirely consistent. In early retinal lesions, structural improvements may precede functional changes. Naturally, macular edema has a substantial impact on vision. Given that our primary objective was to evaluate changes in retinal microvasculature, and changes in macular edema were only a secondary efficacy endpoint, of the 484 enrolled patients, only 78 had macular edema 59 in the treatment group and 19 in the control group. This small number of target events may have limited our ability to detect differences in visual acuity between the two groups. Nevertheless, in future studies, greater emphasis will be placed on assessing the effects of CDDP on visual acuity.

Regarding the study design, we adopted a placebo-controlled approach rather than comparatively assessing an active drug control, e.g., calcium dobesilate, which is currently one of the most commonly used agents in clinical practice with demonstrated efficacy in improving retinal microaneurysms and reducing retinal hemorrhage[23]. Although no direct comparison between the two agents has been performed, studies have shown that their combination yields more pronounced therapeutic effects[2,24], suggesting that this may represent a promising combination therapy option for clinical treatment of NPDR.

In summary, this large-scale clinical trial suggested that CDDP may be a safe and effective option for improving retinal microvascular lesions in NPDR cases, representing a new therapeutic choice for clinical management. Further studies are needed to evaluate long-term outcomes and the potential for slowing vision-threatening conditions.

CONCLUSION

This study indicates that CDDP can significantly, effectively and safely improve the condition, as evidenced by retinal microvascular status, number of hemorrhages, and exudation area, providing a promising intervention for DR patients.